In "The Tell-Tale Heart," what evidence suggests the narrator is insane?

One of the first pieces of evidence that indicates that the unnamed narrator is insane is his obsession with the old man's "vulture" eye. The narrator explains his reasoning by saying,

Object there was none. Passion there was none. I loved the old man. He had never wronged me. He had never given me insult. For his gold I had no desire. I think it was his eye!

The narrator is clearly mentally unstable and even contradicts himself by stating that he "loved the old man." Why would anyone want to murder the person they claim to love? It is also concerning that the old man's pale blue eye is the primary reason the narrator is motivated to kill him.

In addition to the narrator's questionable motive, the narrator also comes across as desperate. The narrator is continually attempting to prove his sanity. Why would a rational, stable person need to convince someone that they are sane? Another piece of evidence that indicates the narrator is insane concerns the syntax of his narrative. The narrator speaks in fragmented sentences, which create a halting cadence that suggests agitation. This makes the narrator come across as neurotic and mentally unstable.

One of the most significant pieces of evidence that indicates the narrator's insanity is the brutality of his crime. The narrator not only stalks and suffocates the old man, but also dismembers his body and places his limbs underneath the floorboards of his home. Only a mentally insane individual would be capable of committing such an atrocious act. The narrator once again displays his insanity by claiming to hear the old man's heartbeat.

Why does the "The Tell-Tale Heart" narrator believe he is not mad?

In Edgar Allan Poe's classic short story "The Tell-Tale Heart," the narrator believes, and wants the reader to believe, that he's not mad because he so perfectly calculated and carried out every step of the murder of an old man, from the conception of the murder to the cover-up.

You should have seen how wisely I proceeded—with what caution—with what foresight—with what dissimulation I went to work!

As further proof that he's not mad, the narrator invites the reader to "Hearken! And observe how healthily—how calmly I can tell you the whole story."

To convince himself and the reader that he's not insane, the narrator explains everything he did in great detail and praises his own persistence—even his courage—in the way he sticks to his plan and never deviates from his goal of ridding himself of the old man and his "Evil Eye."

The eye of a vulture—a pale blue eye, with a film over it.

The narrator wants the reader to understand how fully and how deeply he understands the old man, how he understands the old man's fear, and how he even knows what the old man is thinking.

I knew what the old man felt ... I knew that he had been lying awake ever since the first slight noise, when he had turned in the bed. His fears had been ever since growing upon him. He had been trying to fancy them causeless, but could not. He had been saying to himself—“It is nothing but the wind in the chimney—it is only a mouse crossing the floor,” or “It is merely a cricket which has made a single chirp.” Yes, he had been trying to comfort himself with these suppositions.

The narrator commends himself with how he observes the old man's eye with "perfect distinctness" and how he directs the narrow ray of the lantern to the eye "as if by instinct, perfectly upon the damned spot."

[N]ow, I say, there came to my ears a low, dull, quick sound, such as a watch makes when enveloped in cotton. I knew that sound well, too. It was the beating of the old man's heart.

It's not madness, says the narrator, "but over-acuteness" of his sense of hearing caused by his nervousness, as he says in the opening paragraph of the story.

The disease had sharpened my senses—not destroyed—not dulled them. Above all was the sense of hearing acute. I heard all things in the heaven and in the earth. I heard many things in hell.

The narrator's obsession shifts from the old man's "Evil Eye" to the old man's loudly beating heart. When, finally, he commits the murder, the narrator is concerned much more about the old man's heart than he is about his pale blue, filmy, "vulture eye." In fact, by this point in the story, the old man's eye is little more than an afterthought.

I placed my hand upon the heart and held it there many minutes. There was no pulsation. He was stone dead. His eye would trouble me no more.

He never mentions the old man's eye again.

If still you think me mad, you will think so no longer when I describe the wise precautions I took for the concealment of the body.

Once again, the narrator praises his perfect execution of his plan.

I took for the concealment of the body. The night waned, and I worked hastily, but in silence. First of all I dismembered the corpse. I cut off the head and the arms and the legs.

I then took up three planks from the flooring of the chamber, and deposited all between the scantlings. I then replaced the boards so cleverly, so cunningly, that no human eye—not even his—could have detected any thing wrong.

When police officers arrive to investigate information from a neighbor who heard a shriek during the night, the narrator boldly takes them into the old man's room, the room where he committed the murder.

I led them, at length, to his chamber. I showed them his treasures, secure, undisturbed. In the enthusiasm of my confidence, I brought chairs into the room, and desired them here to rest from their fatigues, while I myself, in the wild audacity of my perfect triumph, placed my own seat upon the very spot beneath which reposed the corpse of the victim.

In time, the narrator's perfect plan is undone by his own nervousness and acute sense of hearing. As he sits in his chair directly above the old man's corpse, he hears the beating of the old man's heart. He first hears the heart beating as if from a distance; then, the sound grows increasingly louder until it seems to fill the room and inhabit the narrator's entire being, causing him unbearable agony.

By the end of the story, the beating heart drives the narrator into raving, raging madness—unless, of course, he was already mad when he started to tell the story.

Why does the "The Tell-Tale Heart" narrator believe he is not mad?

The narrator does not want his listeners to believe that he is mad because he wants what he has to say to be taken seriously and not written off as the ravings of a lunatic. Further, he truly believes that he is not mad, only "nervous." He feels that his nervousness has "sharpened [his] senses—not destroyed—not dulled them." He believes that he can hear "all things in the heaven and in the earth" as well as "many things in hell." Therefore, in his mind, his experiences differ from the average person's not because he is insane but because his senses are more acute, more powerful than ours. Further, he says, "observe how healthily—how calmly I can tell you the whole story." He believes that his ability to remain calm proves how healthy he is. In reality, he doesn't do a very good job of remaining calm at all (notice how many exclamation points crop up during his narration), and the events and feelings he goes on to describe most certainly oppose his claim to sanity.

Why does the "The Tell-Tale Heart" narrator believe he is not mad?

The narrator in "The Tell-Tale Heart" begins by announcing that he is not mad and arguing that nobody could possibly claim that he was. He justifies his argument by pointing to the fact that he can hear everything that is going on—not only in the real world in which he is living but also in heaven and hell. His senses, rather than being diminished by supposed madness or disease, have actually been sharpened. He notes that because he can hear everything that is happening in the earthly world, as well as in heaven and in hell, he cannot possibly be mad but rather is more perceptive than ever before.

The narrator, of course, is obviously mad from the beginning, as Poe's narration makes clear. However, he gives this evidence stating otherwise as a means of trying to convince the reader that what he is saying is true and that he is able to hear and perceive unexpected and surprising things, not because of any inherent madness but simply because his senses have been heightened as a result of his "disease." The narrator seems to recognize, however mad he may be, that he is likely to be disbelieved and dismissed. As such, he provides some reasoning as to why his acute perception of the world around him should be taken seriously.

What evidence does the narrator provide for his claim that he is not mad in "The Tell-Tale Heart"?

In "The Tell-Tale Heart" by Edgar Allan Poe, the narrator provides little real evidence to support his claim that he is not mad, which only serves to convince the reader that he is. In fact, Poe begins the story by having the narrator admit that he has been ill or at least extremely nervous.

True!—nervous—very, very dreadfully nervous I had been and am; but why will you say that I am mad?

The narrator attempts to prove that he is not mad by showing how “cunning” he was and “how wisely” he proceeded with his crime. After all, he reasons, “Madmen know nothing.” In contrast, he knew how to plan his crime and commit it in an ingenious (in his demented mind) way. He says he proceeded “with what caution— with what foresight—with what dissimulation ...” In other words, a madman would not have had the mental acuity to carry out the plan as well as he did.

Moreover, he was patient, another thing that perhaps a madman would not be. He takes “an hour to place [his] whole head within the opening so far that I could see him as he lay upon his bed.” The narrator then asks the reader, “would a madman have been so wise as this?”

He was also calm, according to his telling of the story. The implicit question he asks is whether a madman would have had the ability to commit the crime and maintain his presence of mind and calmness as he did. To explain why his actions might seem mad to some people, he says, “what you mistake for madness is but over-acuteness of the senses.”

He then describes how the “beating of the old man’s heart” was as loud to him as a drum beat because of this “over-acuteness of the senses.” Even though the heartbeat drove him to fury, he nevertheless “kept still.” This is another piece of evidence to show that he was in possession of his mental faculties and not mad.

Finally, after he has killed the old man, he has another point to prove that he is not mad. He says,

If still you think me mad, you will think so no longer when I describe the wise precautions I took for the concealment of the body.

Is the narrator in "The Tell-Tale Heart" guilty and insane?

The narrator is clearly guilty of murder but what is important is that he considers himself sane. The purpose of him narrating the story is to tell the reader of his sanity as indicated by his careful and astute planning of the crime.

I think it is unlikely that the narrator would want to enter a plea of insanity. He may be content to be punished as his plan to evade detection was unsuccessful.

Is the narrator in "The Tell-Tale Heart" guilty and insane?

Because the protagonist so carefully and methodically carried out this murder, it would be difficult for him to obtain the "insane" defense.  He carefully planned his murder and then had made the effort to hide it with great care.  He clearly IS insane, but in a court of law, due to the premeditation and the fact he could think clearly about how he was going to carry it out and dispose of the body, he would probably not be able to claim insanity.

Is the narrator in "The Tell-Tale Heart" guilty and insane?

Although the narrator has indeed committed murder, the question you're asking is whether he is to be considered morally responsible or not. In most Occidental societies, a person truly insane cannot be held accountable for his acts. Execution or a life sentence in prison is waïved for confinement in a psychiatric ward or mental hospital.

So finally, what is the difference? If a person cannot be rehabilitated, he will continue to be a public threat since he acts on impulse rather than reason. A "crazy" person cannot " learn" to be good. Isolation by confinement seems to be the only recourse to keep society "safe" from such specimens....

As to the moral aspect of guilt, this is also a slippery fish to seize. If a person has no control over his acts, he may be considered a dangerous criminal but not "guilty " per se, if guilt is indeed the opposite of innocence. That would be likened to convicting a person of careless driving in a car without brakes or a steering wheel!

There are some famous public trials where the defendent has pleaded insanity or senile debility to avoid prosecution. The Pinochet trials are an example of this; I'm sure with a little research you can find others.

Is the narrator in "The Tell-Tale Heart" guilty and insane?

One of Edgar Allan Poe's most popular short stories is "The Tell-Tale Heart." The question of the narrator's sanity is not unusual especially because he begins his tale by insisting that he is not crazy!

TRUE!—NERVOUS—VERY, very dreadfully nervous I had been and am; but why will you say that I am mad? The disease had sharpened my senses—not destroyed—not dulled them.

The narrator insists he is not mad, but admits that he suffers from the disease of madness. His argument is that rather than being incapacitated in any way, his condition has improved his senses. This conclusion is based upon his insanity for logically one cannot be ill and be better off for it. However, he continues to insist that he is not crazy throughout the story.

The one paragraph that seems to solidify not only his insanity but also his guilt is found below:

It is impossible to say how first the idea entered my brain; but once conceived, it haunted me day and night. Object there was none. Passion there was none. I loved the old man. He had never wronged me. He had never given me insult. For his gold I had no desire. I think it was his eye! yes, it was this! He had the eye of a vulture—a pale blue eye, with a film over it. Whenever it fell upon me, my blood ran cold; and so by degrees—very gradually—I made up my mind to take the life of the old man, and thus rid myself of the eye forever.

Note first that "the idea" has taken ahold of his mind: it haunts him continually. This is clearly obsession in the strictest sense. The "haunting" not only infers that the idea is never out of his mind, but also that he has no control of the idea. This supports the conclusion that the narrator is mad.

Additionally, he recognizes that he has no reason to wish the man ill. He states that he is not driven by passion (anger); there is no desired outcome that he anticipates from the man's death. In fact, he claims that he "loved the old man." He does not harbor any ill feelings toward him, for the old man never harmed him or insulted him. And the speaker does not want the old man's money either. With no valid reasoning present, these statements further convince the reader of the instability of the narrator's mind.

What very neatly supports his insanity is the younger man's obsession with the old man's eye. In his madness, he has fixated on the elderly man's blind, blue eye.

I think it was his eye! yes, it was this! He had the eye of a vulture—a pale blue eye, with a film over it. 

The narrator's paranoia is obvious. He personifies the eye, treating it as if it has a life of its own, apart from the will of the old man. He irrationally believes that the eye is the cause of his distress and only in killing the man can he be rid of it. When entering the man's room in the dead of night, the speaker believes that the eye follows him, but the film over the eye makes this assumption irrational and impossible.

Having established that the man telling the tale is insane, consider if the man is culpable (or accountable) for committing the murder. Could he not be found innocent by reason of insanity?

The insanity plea in a court of law is only useful if it can be established that the madness present prevented the perpetrator of the crime from distinguishing between right and wrong. More specifically put, the definitive measure of insanity was based upon the trial of Daniel M'Naghten in England in 1843. M'Naghten murdered the Prime Minister's secretary because he believed the Prime Minister was "conspiring against him." Findings in this case became the standard measure for insanity, and are still used in U.S. courts:

The "M'Naghten rule"...created a presumption of sanity, unless the defense proved "at the time of committing the act, the accused was laboring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing or, if he did know it, that he did not know what he was doing was wrong."

The narrator did know that what he was doing was wrong, and fully comprehended exactly what he was doing.

Certainly the murder is premeditated. The man announces to the reader that once he ascertained (erroneously) that the eye was the source of his difficulties, he immediately decided that he had to kill the man to be free from its non-functioning gaze. There also can be no doubt that the narrator knew the difference between right and wrong—knew that he was committing a crime.

First of all, he does not want the old man to cry out and alert the neighbors—who would, ostensibly, call the police. Then he hides the body. (Actually, he literally crows with delight while recounting how brilliantly he disposed of the evidence of his deed.) He buries all beneath the floorboards in an attempt to conceal what he has done.

When the police eventually arrive, he pretends that all is well. He invites them in to search the house. He explains that the old man is in the country. He even takes the men into the old man's room and with insane arrogance invites them to sit, rest and chat even while the body parts rest squarely beneath their feet.

Here again his madness is glaringly apparent in that soon thereafter he is convinced that he hears the beating of the dead man's heart. (He is delusional). He soon becomes excessively agitated, while also noticing that the policemen seem oblivious to his discomfort while the sound grows ever louder in his ears. Ultimately, with paranoia bursting from within him, he is certain that the men are well aware of what he is done and they are "making a mockery of [his] horror."

All at once, he begins to rave in his madness:

I felt that I must scream or die! and now—again!—hark! louder! louder! louder! louder!

“Villains!” I shrieked, “dissemble no more! I admit the deed!—tear up the planks! here, here!—It is the beating of his hideous heart!”

The narrator is not only insane, but he is also guilty of murder.

In "The Tell-Tale Heart," whose heart does the narrator hear? What does this suggest about their sanity? When does the narrator seem to lose their sanity?

At the end of the story, the narrator hears his victim's heart beating underneath the floorboards. His heightened sensitivity to imagined sounds demonstrates his paranoia and mental instability. It's also possible he mistakes the sound of his own accelerating heartbeat for the dead man's. As to what point in the narrative the narrator begins sounding and acting mad, it can be argued that he reveals his acute psychosis from the beginning of the story. For example, he asserts that his feelings of enmity stem from his hatred of the old man's "pale blue eye." He then maintains that he will kill the old man in order to rid himself of the eye "forever." Essentially, the narrator demonstrates his mental deterioration by proclaiming that a human being can be separated into distinct and autonomous parts.

The word "sublime" means exalted or awe-inspiring. Poe viewed the sublime as the inclusion of light and dark. In his interpretation of the sublime, obscurity and power had equal emphasis. Poe was interested in how his verbal descriptions could make his readers perceive objects on a more visceral level than an academic one. His conception of beauty embraced all the elements of ideality (perfection): the sublime, the grotesque, the arabesque, and the picturesque. Additionally, Poe's idea of the sublime challenged the rational order of things (remember that light and darkness had equal emphasis in Poe's world). 

If Poe's sublime challenged rationality, it is conceivable that his stories would be imbued with elements of irrationality or mental deviance. In "The Tell-Tale Heart," Poe has created a world where the surreal mingles with the lucid. The narrator perceives the old man as both a physical being as well as a conglomerate of body parts. He does this from the beginning of the narrative, when he proclaims his desire to kill the old man in order to be rid of his "Evil Eye." Essentially, Poe's idea of the sublime incorporated the interaction between light and darkness in the human soul.

It is true that some critics have suggested that Poe's narrator is a woman. Our perception of the narrator largely depends upon our biases and preconceptions about gender. For example, are we more inclined to feel sympathy towards a female narrator? If so, are we then more predisposed to the idea of the narrator as the victim rather than the cold perpetrator of a horrendous crime? Is it conceivable for a woman to kill someone she loved? If so, how could she justify it? These are just a few of the questions we can ask ourselves as we ponder the ramifications of this unique short story.

Source:

Edgar Allan Poe: The Sublime, the Picturesque, the Grotesque, and the Arabesque, Frederick L. Burwick, Amerikastudien / American Studies, Vol. 43, No. 3, The American Sublime (1998), pp. 423-436.

What quotes from "The Tell-Tale Heart" prove the narrator's sanity?

The main difficulty in answering this question is that, as currerbell16 points out, the narrator of "The Tell-Tale Heart" by Edgar Allan Poe is rather clearly not sane. In fact, the very efforts by the narrator to convince us of his sanity contribute to our doubts about his mental stability. Instead, what we should look at is how the narrator's attempts to convince us that he is sane actually contribute to our conviction that he is not sane. 

The story opens by raising the issue of sanity. The narrator states:

TRUE! —nervous —very, very dreadfully nervous I had been and am; but why will you say that I am mad? The disease had sharpened my senses ... Above all was the sense of hearing acute. I heard all things in the heaven and in the earth. I heard many things in hell. How, then, am I mad?

First, the narrator seems to be responding to an interlocutor who has accused him of being mad. Thus we are confronted with a choice of whether to trust the narrator or the unknown interlocutor on this point. The immediate admission that the narrator is "very, very, dreadfully nervous" inspires immediate doubts, and his claim to be able to hear all things in heaven and earth and even some in hell, far from being proof of sanity, show the narrator to be out of touch with reality.

The next type of evidence that the narrator gives is the cleverness with which he plotted against the old man. He states:

You fancy me mad. Madmen know nothing. But you should have seen me. You should have seen how wisely I proceeded —with what caution —with what foresight —with what dissimulation...

While on the one hand, the narrator argues that all of this patient plotting is evidence of his sanity, the idea of carefully plotting to kill a kind, feeble, elderly man who has never harmed the narrator is itself insane.

The final piece of evidence the narrator gives for his sanity is the way he carefully dismembered the body and placed it under the floorboards. Realistically, though, after several hours, the body would begin to decompose and the odors (as well as the insects and vermin it would attract) would give its presence away. Thus this is not only insane but not very clever.

Why does the narrator in "The Tell-Tale Heart" claim he's nervous but not mad?

The narrator wants his audience to believe that he is not mad, seemingly as some sort of defense against his actions. Interestingly, he presumes that his audience has already determined his lack of sanity:

How, then, am I mad?

There is an implication in this line that he stands accused of madness, and this story is an attempt to clarify a misunderstanding of his character. He may be nervous—"very, very dreadfully nervous"—but he insists that this is not madness. He points to the fact that he can "calmly" tell the entire story of the way he murdered an old man—a crime committed for no reason other than the appearance of one of the old man's eyes.

The narrator explains that in his constant, dreadful state of nervousness, his sense of hearing has become especially acute. This is an important detail because in the end, the narrator claims that after his murder of the old man, he could still hear the man's heart beating. On some level, the narrator has an understanding that this is impossible; after all, he had dismembered the man and placed the pieces underneath the floor. Yet he clings to the belief that his perception is possible because of the heightened senses he has gained through his chronic nervousness, ignoring the reality that it is impossible to hear the heartbeat of a dead and dismembered man.

The narrator wants to build credibility and understanding through classifying himself as nervous instead of mad.

In the story "The Tell-Tale Heart," is the narrator insane? Does his insanity as evidence that he is not guilty of the crime?

There is insanity, and there is criminal insanity.

The narrator of this story is clearly delusional, having hallucinations, and out of touch with reality as we understand it. He tries to explain that he is sane in ways that only convince us, ironically, that he is out of his mind. No person who is connected to reality would murder an old man because they think he has an evil eye. No rational person would believe they heard the loudly pounding heart of a man dead and buried.

But this behavior, while it might warrant quite a bit of psychiatric help, does not rise to the level of criminal insanity that would alleviate the narrator of guilt. The narrator would have had to convey in the story, convincingly, that he had no idea what he was doing or that it was wrong. If he were convinced that the old man was, say, a head of lettuce that he needed to chop up for his salad and was able to persuade people that he really didn't know in the first place that he was murdering or attacking a human being—if he were that detached from reality—he might well not be guilty by reason of insanity.

However, the narrator clearly communicates that he does know the old man is a human, states that he kills him, and shows enough understanding of the legal consequences of his act to hide the body and try to deceive the police. He knows what he did is wrong in the eyes of society. The only reason he confesses is because he thinks the police hear the heart too and are mocking and playing with him. A person with such an awareness of what he has done and the implications of the deed is not criminally insane.

In the story "The Tell-Tale Heart," is the narrator insane? Does his insanity as evidence that he is not guilty of the crime?

If the narrator were truly insane, he probably would not be able to relate the circumstances of the story or to feel anxiety at the visit of the detective. Since the presence of the detective makes him increasingly uncomfortable, we can surmise that he is feeling guilty and anxious about the possible discovery of his crime. Despite his crimes, the narrator obviously feels that he is responsible and that on some level he deserves punishment. The calm smiling demeanor of the detective unhinges him, showing his paranoia and nervousness, until he can stand it no longer and insists on tearing up the floorboards. This is his way of wanting to confess his crimes and suffer the consequences, proving he understands the moral implications of his actions, which proves he is sane.

How does the narrator of "The Tell-Tale Heart" try to prove his sanity, and where is it questioned?

The narrator of Edgar Allan Poe's story opens the tale by insisting that he is not only sane, but also stronger because of a recent illness that has rendered his "mind ... feelings ... senses stronger, more powerful." In particular, he claims that his "sense of hearing especially became more powerful." A thoughtful reader will understand right away that the narrator's protestations of his sanity are a red flag that something is wrong with his thought process. Generally speaking, people who are well-adjusted and healthy don't need to verbally affirm their mental fitness. The narrator, however, assures his audience that he will, in fact, prove "how healthy [his] mind is."

Readers' suspicion that the narrator is indeed insane is confirmed when he explains that because he found the old man's eye disturbing and vulture-like, he knew he had to kill him. He tries to rationalize his irrational act and, in doing so, offers irrefutable proof of his derangement. He employs a logical fallacy by claiming "a madman cannot plan" and then proceeds to describe how he stalked the old man for several nights and watched him sleep until the night he murdered and dismembered him. He is strangely proud of his stealth and ruthlessness and displays neither pity nor compassion for his elderly and helpless victim.

Ultimately, the narrator's belief that he can hear the heart of his victim beating through the floorboards is his undoing. His departure from reality is complete as he shouts his confession.

How does the narrator of "The Tell-Tale Heart" try to prove his sanity, and where is it questioned?

In “The Tell-tale Heart” the narrator seems to believe that the reader doubts his sanity, because he is constantly asking if we think he’s mad and reminding us that he is not.

The narrator tries to convince us he is not insane.

1. Just as he begins the story by making us think he is mad, the narrator also begins the story by insisting that he is not.

The disease had sharpened my senses—not destroyed—not dulled them. (enotes etext p. 4)

He tries to convince us that the sickness has not hurt his sanity.

2. The narrator goes on to explain that he is not mad because “madmen know nothing,” yet he is brilliant.  He tries to convince us of his brilliance.

But you should have seen me. You should have seen how wisely I proceeded—with what caution—with what foresight—with what dissimulation I went to work! (p. 4)

The narrator explains that he kept peeking in on the old man and the old man had no idea.

3. The narrator explains how clever he was when the police arrived, and he led them right to where the body was and had a nice conversation with them.

I brought chairs into the room, and desired them here to rest from their fatigues, while I myself, in the wild audacity of my perfect triumph, placed my own seat upon the very spot beneath which reposed the corpse of the victim. (p. 6)

The narrator explains that the police never suspected him, but it is likely they did.  Why else would they stay and chat with this guy?  They were just waiting for him to crack.

Yet we doubt the narrator’s sanity.

1. The narrator’s sanity is called into question immediately.  As the story begins, the narrator is demanding why we think he’s mad.

[Very] dreadfully nervous I had been and am; but why will you say that I am mad?  (p. 4)

By bringing up a disease right away, the reader begins to think that there really is something wrong with the narrator.  He might have gotten sick and that caused him to lose his mind, or he might be describing mental illness.  The narrator brags about how calmly he can tell the story.

2. We also question the narrator’s sanity when he explains why he had to kill the old man.  It was the old man’s eye, of course.  The narrator becomes obsessed with it.

Whenever it fell upon me, my blood ran cold; and so by degrees—very gradually—I made up my mind to take the life of the old man, and thus rid myself of the eye forever. (p. 4)

To fixate on an old man’s eye, and want him dead for no reason, is clearly crazy.  The narrator admits that he has nothing against the man except that eye.

3. Of course, when he kills the old man we know he’s crazy.

If still you think me mad, you will think so no longer when I describe the wise precautions I took for the concealment of the body. The night waned, and I worked hastily, but in silence. First of all I dismembered the corpse. I cut off the head and the arms and the legs. (p. 5)

No sane person would hide a body under the floor.  Obviously it will begin to smell!  Clearly we are not convinced that the man is sane, and his continual protests that he is not mad just convince us that he is.

Text:  http://www.enotes.com/tell-tale-heart-text

How does the narrator in "The Tell-Tale Heart" try to prove his sanity?

As your question already notes, the narrator in Edgar Allan Poe’s short story “The Tell-Tale Heart” seems very defensive about being called mad. In the very first sentence, he addresses the issue. As the tale proceeds, he brings up madness again and again. It’s almost if the narrator is on trial. Instead of proving to a judge or jury that he’s sane, he has to prove to the reader that he’s not a madman.

For the narrator, madness is almost synonymous with stupidity. At one point, the narrator claims:

Madmen know nothing. But you should have seen me. You should have seen how wisely I proceeded—with what caution—with what foresight—with what dissimulation I went to work!

For the narrator, his careful, patient, mindful murder of the elderly man seems to function as proof that he’s not insane. Actually, the narrator is quite calculating and strategic. The concealment of the corpse provides further proof of the narrator’s craftiness and cunningness—traits that, apparently, rule out madness.

Another argument taken up by the narrator involves his senses. The narrator seems to claim that people tend to confuse madness and people with extraordinarily acute senses. To prove this argument, the narrator draws attention to how sharply aware he is of sounds, especially the sound of the old man’s beating heart.

Unfortunately for the narrator, his own hyper-developed senses seem to do him in. When the police arrive, the narrator’s ability to still hear the beating heart drives him to confess. Perhaps you could argue that the confession upends the narrator’s claims that he’s not mad, though the narrator would argue otherwise.

Why does the narrator in "The Tell-Tale Heart" claim he isn't mad?

Edgar Allan Poe's short story "The Tell-Tale Heart" is told by a first-person narrator, and the line to which you refer is found in the first paragraph, though your quote, as written in your question, is not quite correct. The narrator talks directly to us, and he begins his story this way:

True!--nervous--very, very dreadfully nervous I had been and am; but why will you say that I am mad? The disease had sharpened my senses--not destroyed--not dulled them. Above all was the sense of hearing acute. I heard all things in the heaven and in the earth. I heard many things in hell. How, then, am I mad? Hearken! and observe how healthily--how calmly I can tell you the whole story.

This reference to madness comes as the answer to an unasked question, or perhaps the response to an unspoken remark. The narrator in some way anticipates that his listeners (readers) might possibly think he is mad (crazy); however, before we can say it, he tells us we we would be wrong to make that assumption. It is the first of at least four such statements, statements in which the speaker dismisses the idea that he could possibly be mad.

The next reference to his non-existent (according to him) madness happens several paragraphs into the narrative. The speaker says:

Now this is the point. You fancy me mad. Madmen know nothing. But you should have seen me. 

The narrator is admitting the reality that his listeners (readers) probably do think he is mad, but he takes great pains to detail all the precise and well planned things he does to carry out his intention to rid himself of the man--and therefore the eye. Those details actually help confirm our suspicions about the speaker's mental state.

The next reference to madness is spoken by the narrator just before he recounts the actual murder of the man.

And have I not told you that what you mistake for madness is but over-acuteness of the sense? 

Here he actually tells his readers that they probably do think he is mad, but he endeavors to convince us that what we think is madness (something decidedly negative) is actually a blessing called heightened sensitivity (something generally considered to be positive). We, of course, have been reading his horrific, mad story and are not convinced.

Finally, the murder has been committed and now the narrator is going to try to convince us that he is not mad by demonstrating his cunning craftiness as he ingeniously disposes of the body.

If still you think me mad, you will think so no longer when I describe the wise precautions I took for the concealment of the body. 

Obviously anyone who murders a man, especially just because he is "creeped out" by the man's eye, has got our vote as a madman, and only a madman would take pride in figuring out how to flawlessly conceal the body.

The narrator asks an important question in the first line of this story: "but why will you say that I am mad?" Ironically, despite his attempts to persuade us he is not crazy, the narrator spends the rest of the story proving why, exactly, we will say that he is mad. 

Is the murderer in "The Tell-Tale Heart" sane or insane?

It is not generally regarded as a characteristic of sanity to keep insisting, with increasing vehemence, that one is not mad. The narrator of “The Tell-Tale Heart” not only does this but even accuses the reader of thinking him mad, an accusation he repeats four times throughout the course of a very short story.

Other evidence of the narrator’s madness includes his extremely tenuous justifications for the murder.

Object there was none. Passion there was none. I loved the old man. He had never wronged me. He had never given me insult. For his gold I had no desire. I think it was his eye! yes, it was this!

In this quotation, it seems as though his distaste for the old man’s eye has only just occurred to the narrator, but he adopts it as his reason for murder and henceforth insists upon it with all the dogmatism of madness. His description of his preparations for the murder also seem unbelievable to the point of insanity. He keeps referring to the slowness of his movements and once says that he took an hour to put his head around the door. He says that he could not kill the old man on the first seven nights because his eye was closed (scarcely surprising, since he was asleep); but by waiting until the old man is awake, he loses the element of surprise, which was the point of killing him in the middle of the night. Finally, of course, there is the matter of his hearing a deafeningly loud heartbeat emanating from a corpse.

Altogether, the feverish, rambling, paranoid style of the narrator and the lack of motive and method in his murder suggest that, if not actually insane, he is very close to madness.

What are the indicators of sanity and insanity in the narrator from "The Tell-Tale Heart"?

One major clue that the narrator is, in fact, insane is that he decides that he must kill an old man that he "loved" for no other reason than the old man's "vulture" eye. He says, "Whenever it fell upon [him], [his] blood ran cold [. . .]," and this is certainly not a sane response to someone's eye. It's likely that the old man has cataracts, which would account for the eye's paleness and the appearance of a "film over it," and this might be creepy-looking or strange, but it would not be murder-inducing to a sane person.

Further, much of what the narrator says to prove that he is sane actually makes him seem more insane. He talks about "how wisely [he] proceeded" with his plot to kill the old man. He says that he was "never kinder" to the man than he is during the day while, each night, he creeps into the old man's bedroom with a plan to kill him. This attention to detail and "caution," as he calls it, only make him seem more mad. He talks about how slowly he moved his head into the room, insisting, "Would a madman have been so wise as this . . ." This line of argument has the opposite effect from that which he intends.

On the other hand, the narrator talks about his own fears concerning death, and this is a pretty rational fear. He describes the awful moan made by the old man on the fateful night:

I knew it was the groan of mortal terror. It was not a groan of pain or of grief—oh, no!—it was the low stifled sound that arises from the bottom of the soul when overcharged with awe. I knew the sound well. Many a night, just at midnight, when all the world slept, it has welled up from my own bosom, deepening, with its dreadful echo, the terrors that distracted me.

He admits, then, that his fear of death has actually kept him awake at night. Further, this is probably why he needs to kill the old man: the old man reminds the narrator of death because of his age, his disease, and the "vulture" look of his eye (and vultures are associated with death). So, while his fear of death may be a sane one, his response to that fear is insane.

What are the indicators of sanity and insanity in the narrator from "The Tell-Tale Heart"?

In Edgar Allan Poe's "The Tell-Tale Heart," a narrator tells the story of an old man he is caring for, whom he eventually kills. From the start, he addresses the reader (by using second person-you) saying that the reader may find him to be very nervous. By the end of the story, his guilt over the murder has caught up with him and he confesses to the crime. There are many examples in the story that support a reading of the narrator being sane and also insane.

The points that show the narrator as sane include his explanation of the time and days, as well as the steps he took to commit the crime. He seems logical in this explanation, even though his motivation may be problematic. The examples that point to his insanity are his insistence on killing the old man while the eye is open and the heartbeat he claims to hear throughout the story. Because we know that there is no way he can hear a dead man's heartbeat, this is perhaps the strongest example that points to the narrator's insanity.

Is the narrator of "The Tell-Tale Heart" mad? Why or why not?

It's usually a good rule of thumb in literature that when a first-person narrator assigns himself a virtue, the reader should be instantly suspicious. At the very beginning of  "The Tell-Tale Heart," the narrator responds to what are apparently questions about his sanity by saying:

...but why will you say that I am mad? The disease had sharpened my senses--not destroyed --not dulled them. Above all was the sense of hearing acute. I heard all things in the heaven and in the earth. I heard many things in hell. How, then, am I mad?

He insists he is sane because he can "calmly" tell his story. To him, a display of calm is therefore an indicator of sanity. He also names "foresight" and "caution" as attributes of sanity, divorcing these traits from the actual actions he takes, as if calmness, foresight, and caution alone, even if applied to irrational and sociopathic acts, constitute sanity.

Ironically, his opening lines protesting his sanity lead us to strongly suspect from the outset that he is insane, as he says "I heard many things in hell." Sane people generally don't hear from hell.

As we trace the story out, we come to understand that, even by the narrator's own definition, he is anything but sane. He does not respond to events "calmly" or with "foresight" but in a frenzied, overwrought way. Most notably, while he recounts the caution and premeditation with which he enters the old man's room every night, the murder arises from anything but a calm or cautious state of mind. The narrator expresses his "fury" at the man's heartbeat and states:

And now a new anxiety seized me--the sound would be heard by a neighbour! The old man's hour had come! With a loud yell, I threw open the lantern and leaped into the room.

There are too many instances of the narrator's actions, which he uses to define his sanity, ironically demonstrating madness to recite them all, but one example would be the following:

If still you think me mad, you will think so no longer when I describe the wise precautions I took for the concealment of the body. The night waned, and I worked hastily, but in silence. First of all I dismembered the corpse. I cut off the head and the arms and the legs.

It may or may not have been "wise" to dismember the corpse, but murdering a man for no apparent reason beyond the sound of his heartbeat and dismembering the body are not the actions normally associated with a sane person.

At the end of the story, the narrator also is anything but calm, wise, cautious, or full of foresight, so by his own definition of sanity, he condemns himself:

Almighty God! --no, no! They heard! --they suspected! --they knew! --they were making a mockery of my horror! --this I thought, and this I think. But anything was better than this agony! Anything was more tolerable than this derision! I could bear those hypocritical smiles no longer! I felt that I must scream or die! and now--again! --hark! louder! louder! louder! louder!

"Villains!" I shrieked, "dissemble no more! I admit the deed! --tear up the planks! here, here! --It is the beating of his hideous heart!"

Beyond whether or not he displays certain characteristics associated with sanity, his actions--murder, dismemberment, and finally a frenzied confession based on an imagined sound of a beating heart in a corpse--indicate his madness.

What does the narrator's first paragraph suggest about his sanity in "The Tell-Tale Heart"?

In the first paragraph, the narrator says a few things that lead us to question his mental stability.

First, he admits that he has a "disease" but that it has sharpened his senses. He proclaims that his mental acuity is not dimmed on account of this malady. The narrator's insistence that his disease has not affected him negatively inspires us to harbor skepticism about his veracity. After all, how can physical or mental debilitation or weakness sharpen one's senses? What the narrator says doesn't make any sense.

Next, he claims that his condition has strengthened his sense of hearing. He insists that he can now hear everything that goes on in heaven and on earth. The narrator also maintains that he has heard many things in hell. His preposterous claims lead us to question his sanity.

Lastly, he claims that his calm retelling of a still-obscure story (which will commence immediately) is proof of his health and sanity. His reasoning is flawed, however: we cannot conclude that an individual is sane just because they tell a story calmly.

What is the narrator's first argument that he isn't insane in "The Tell-Tale Heart", and how do his examples counter this claim?

At the beginning of Poe's "The Tell-Tale Heart," he anticipates the reader's assumption that he has gone mad: "But why do you say that I have lost control of my mind, why do say that I am mad?" He attempts to refute this conclusion by declaring that his mind has never been clearer:

Can you not see that I have full control of my mind? Is it not clear that I am not mad? Indeed, the illness only made my mind, my feelings, my senses stronger, more powerful. My sense of hearing especially became more powerful.....I heard sounds from heaven; and I heard sounds from hell!

The narrator's proud assertion that his hearing is so powerful that he is now able to hear sounds from hell suggests that he has completely lost touch with reality, if it was ever within his grasp.

He describes his fear of the "evil eye" of an old man which reminds him of that of a vulture. He is so terrified, in fact, by the man's eye that he has become obsessed by the idea that he must shut this eye forever by killing him. Again fearing that this might strike his reader as evidence of madness, he offers as evidence of his sanity the patience and restraint which he planned the murder of the old man.

With the sound of the old man's beating heart resounding like thunder in the maddened ears of the narrator, he finally murders him by suffocation. Yet again, he congratulates himself on his sanity by commending the extreme care with which he dismembered the man's corpse and concealed it beneath the floorboards.

But finally, when the police arrive to search the premises after being alerted by a neighbor, it's the narrator's madness-induced heightened power of hearing that reveals the evidence of his crime.

What are three evidences of sanity in the narrator of "The Tell-Tale Heart"?

Evidence there might be, but the evidence pointing to the narrator's insanity is more reliable.  Still, that's not the question you asked, so let's see what we can make of it.

First, while we can't put much stock in the character's own assertions of sanity, his rational does make some sense.  "Madmen know nothing," he says, going on to describe in detail the preparations he made for doing away with the old codger. He has a point.  His ability to calculate and plan could be seen as evidence that he is not insane.

Secondly, he is able to understand right and wrong. This is very important, as it is often the crux of an insanity defense.  He knows that what he is doing is wrong because he takes care to dismember and hide the body.  Were he truly insane, the concept of right and wrong would elude him and he wouldn't go through such efforts to avoid detection.

Thirdly, guilt. The level of guilt he feels is enough to cause him to confess at the end of the story, even though he has every chance of getting away with the crime.  Guilt shows a certain level of conscience, and this is not a hallmark of the insane.

I suppose it depends a lot on the definition of insanity.  Most of us would call him crazy, but legally it could be argued that he's not.  A crazy person would act on impulse, not attempt to conceal the crime, and not feel guilty about it.  The narrator here defies all these conventions.

What are three examples that reveal how the narrator of "The Tell-Tale Heart" is insane?

Good question! We get the general impression that the narrator has totally lost touch with reality, but what evidence can we point to that supports this idea? Let's see:

1. "True!—nervous—very, very dreadfully nervous I had been and am, but why will you say that I am mad?"

Here, the narrator is saying, "Yeah, yeah, I'm nervous, but—crazy? No, not crazy!" The fact that he's denying that he's crazy ("mad") is a good hint that he truly is crazy. Why else would he bring it up, or be so defensive about it?

2. "I loved the old man. He had never wronged me. He had never given me insult. For his gold I had no desire. I think it was his eye! yes, it was this! He had the eye of a vulture—a pale blue eye, with a film over it."

In the quote above, the narrator is saying that the old man is a good guy, a friend even, and there's no reason to hate him or want to kill him. Yet he's got a weird-looking eye. That's insane! Sure, someone's physical flaw might creep you out or make you feel uncomfortable, but if you're in your right mind, that flaw won't make you want to kill that other person.

3. "You fancy me mad. Madmen know nothing. But you should have seen me. You should have seen how wisely I proceeded—with what caution—with what foresight—with what dissimulation I went to work!"

Here, the narrator is saying, "Well, you think I'm crazy, but I'm not, because look how carefully I planned this murder!" This is both funny and a perfect example of insane reasoning. You can't disprove craziness by pointing out how detailed the murder plan is. That just supports the idea that the narrator has lost his mind.

The narrator in "The Tell-Tale Heart" is a murderer. What are examples of his insanity?

For one, he visits the old man's room nightly and stares into the dark at him.  He obsesses on the man's eye, "that hideous eye!" He does not feel compassion for the fear the man must be feeling when, night after night, he lies in bed awake and listening for a sound to prove or disprove the presence of another human being.

The killing is planned and premeditated.  It is also sudden.  The narrator worries about the old man's screams, and he prides himself on his clever hiding place of the man's remains: the floorboards of his bedroom.

Perhaps the most telling evidence of insanity is the heartbeat he swears he hears.  It grows louder and louder while the police are there to investigate until the narrator finally breaks down and confesses to the murder.

Based on "The Tell-Tale Heart," is the narrator a guilty murderer or mentally ill?

There are several ways to look at this question, and a number of slants and contexts within the narration itself to inform your answer. The premise of the question seems a little "either/or" to me; it's reductive, in other words. In crime fiction, it’s unusual that the dirty deed is foretold in the first two paragraphs. Poe was among the innovators of detective fiction, though, so he was in advance of the formulae of various narrative conventions.

In film, a character’s mentality must be outlined more plainly; the comparison or contrasts between good versus evil must be stated in high relief. But there’s an ambiguity in this story that’s more sophisticated or "of depth" than it would be if it were acted out instead. Gothic literature is often concerned with a character’s inward being, often as manifested metaphorically, symbolized by wild settings, intense bad weather, or natural forces. The irrational is presented as awesome and shocking, but essentially as an external thing that creates bestial behaviors.

Here, murderous intent becomes the readers’ gateway or lead-in to the plot as it plays out. It’s comparably rarer, fictionally, to have the inward turmoil and struggles of a character presented as a monologue in what would be "real time." The murderer "reasonably" explains that he’s been driven to the act, and his questionable, contradictory logic flows from there. Since his thought processes and actions are appalling, this contrasts with his insistence that he’s being somehow hyper-rational even as he anticipates his listener’s reaction is of his guilt. “But why will you say that I’m mad?”

This twisted logic turns in on itself. He is innocent, if you accept that it’s the old man’s eye that constitutes the presence of evil. But, I’d hardly characterize him as a misguided "innocent." The murder was premeditated. His cluelessness to the bad karma he’s putting out into the world makes him what’s called an “unreliable narrator.” He is, therefore, perhaps, communicating the opposite of what he thinks he means.

To borrow another illustration from film, actors that specialize in villainy have pointed out that evil is in the eye of the beholder; everyone really sees themselves as the heroes in their storyline, as opposed to seeing themselves as morally in the wrong.

Why does the narrator in "The Tell-Tale Heart" claim he is not mad at the start?

A consideration a reader makes when reading a work of literature is whether the narrator is reliable. If the reader feels that the narrator is reliable, then the account of events will be credible. Moreover, the narrator's perceptions of other characters will be accepted by readers as being accurate.

If, on the other hand, the narrator is deemed unreliable, the story he or she tells becomes suspect. Readers understand that the narrative is being manipulated by the narrator for any number of reasons: the narrator is naive or childlike; the narrator is a braggart or self-aggrandizer; the narrator lies because (s)he has something to hide; the narrator is a joker; or, the narrator is mentally unstable.

Poe has his narrator profess his sanity so that the story's outcome is all the more surprising or shocking. He is a murderer, but if he confess it early on, readers might put down the story unfinished.

Why does the narrator in "The Tell-Tale Heart" claim he is not mad at the start?

The narrator of "The Tell-Tale Heart" by Edgar Allan Poe is, as we discover as we read through the narrative, clearly insane by our standards. He also has an obsession with convincing us of his sanity, and emphasizing his rationality and intelligence.

From the point of view of the narrator, the story is almost an argument proving that he is sane, by giving examples of he cleverness and planning. Thus he sets out his point, that he is not insane, at the beginning of the story and then tells a narrative with concrete examples that are intended to prove his sanity.

From the point of view of the reader, the way the narrator repeatedly insists that he is sane gives us our first clue that the narrator is, in fact, insane. People who are normal and sane by the standards of their cultures do not need to insist on their sanity.

What evidence in "The Tell-Tale Heart" suggests the narrator is a madman?

It's a good bet that when someone tries desperately to convince another that he is NOT mad, then the likelihood exists that he probably is. Such is the case with the narrator of Edgar Allan Poe's classic horror story, "The Tell-Tale Heart." In the first sentence, the narrator admits that he is "very, very dreadfully nervous," but then asks the reader if this alone makes him mad. He then claims to hear "all things in heaven and in the earth" as well as "many things in hell." Again, he questions his own sanity. The first lines solidify the likelihood that he is indeed insane.

Although he claims to have "loved the old man," the narrator's desire to kill him because of the evil eye--the "eye of a vulture"--again shows how he teeters on the edge of madness. The thoroughness with which the narrator prepares to kill the old man does not necessarily show his sanity; it instead displays his single-minded goal of murder. Once he accomplishes the act, the gruesome dismemberment only strengthens the argument. The final display of audibly detecting the dead man's still-beating heart is the clue which cements the certainty of his total derangement.

In "The Tell-Tale Heart," what characteristics imply the narrator's insanity regardless of his sanity claim?

I have had to assume you are referring to "The Tell-Tale Heart" as your question did not specify which of Poe's short fiction you were thinking of. Certainly it is this story where the narrator protests most vociferously to being sane where so much evidence is presented to undercut this idea. I think there is ample evidence from the very first paragraph of the story to suggest that the narrator is clearly mad:

True! - nervous - very, very dreadfully nervous I had been and am; but why will you say that I am mad? The disease had sharpened my senses - not destroyed - not dulled them. Above all was the sense of hearing acute. I heard all things in the heaven and in the earth. I heard many things in hell. How, then, am I mad? Hearken! and observe how healthily - how calmly I can tell you the whole story.

There are a number of elements in this first paragraph that display the narrator's madness. First and foremost how the rest of the story deliberately proves that the narrator cannot tell the rest of the tale "calmly," as he himself says he can. In addition, the phrase "I heard all things in the heaven and in the earth," clearly indicates that on some level he is hallucinating - nobody can hear in such a keen manner. The fact that he hears "many things in hell" also establishes that he is perhaps diabolical in his madness, foreshadowing his grim and grisly act of murder.

Do you think the narrator of Edgar Allan Poe's "The Tell-Tale Heart" is crazy? Why or why not?

I would say anyone who kills a person over his eye is probably a bit insane! In "The Tell Tale Heart" by Edgar Allan Poe, the narrator asks in the first sentence, "...but why will you say that I am mad?" (Poe 1) He goes on to give all the reasons why he should NOT be considered mad, but he is none too successful. The narrator says that "Madmen know nothing," (Poe 1) and therefore he cannot be mad because he  carefully planned out the execution (!) of his plan. He proceeds to show us just how crazy he really is.

The narrator of the story tells us that he loved this man, but he could not stand his eye. People do not kill someone they love over their eye. That's crazy. On the night he killed the old man, he said he could hear the man's heart beating louder and louder, and later when the police officers are there, he begins to hear it again, though the man is dead. In the end, his craziness forces him to confess.

What do the narrator's repeated sanity claims in "The Tell-Tale Heart" reveal about his character?

The narrator's repeated assurances to the reader that he is sane reminds me of the Shakespeare quote regarding "... thou dost protest too much, methinks." Why would a sane man have to constantly defend his sanity unless he already suspects that he might be descending into madness? His reasoning is jumbled: He claims that the owner of the house has never hurt him, yet he decides he must kill the innocent old man. It is the old man's evil eye, the narrator claims, that forces him into killing him. He admits that he is "very dreadfully nervous" for no other apparent reason than the old man's eye. And he admits to a disease that "sharpens" his mind. Perhaps it is not the old man's eye, but

... the narrator really wishes to destroy the "I," that is, himself... by destroying the old man's eye, the narrator indirectly destroys himself in the end by exposing himself as the murderer. (eNotes, "The Tell-Tale Heart," Themes and Characters) 

Little of the narrator's reasoning is sound. He makes detailed preparations for the murder and practices for days, but when the hour comes, his "foresight" fails to quietly subdue the old man. The solitary scream that is heard by a neighbor seals his fate. In addition to being a madman, our storyteller is also an unreliable narrator, one whose words must always be called into question.

Why does the narrator in "The Tell-Tale Heart" insist he is nervous, not mad?

In "The Tell-Tale Heart," the narrator clarifies that he is nervous, not mad, because he wants to make his story sound credible.

He knows that if anyone thought for one moment that he was mad, then they wouldn't believe a word of his story. It would be regarded as nothing more than the ravings of a madman, easily ignored and just as easily rejected.

The narrator presumes that his audience already thinks he's mad. After all, the hideous crime he's committed, the senseless murder of an old man, would seem to indicate insanity on his part. That being the case, it's all the more important for the narrator to go out of his way to convince his audience that, contrary to what they might think, he really isn't mad after all.

Claiming that he's nervous rather than mad also allows the narrator to account for some rather bizarre details concerning the murder. For instance, he claims that it is his nervousness that's responsible for his acute hearing. In turn, it's supposedly because of this that he's able to hear the beating heart of the old man even after he killed him.

However, no one could seriously be convinced of the narrator's efforts to make himself out to be nervous rather than mad. No matter how acute one's hearing may be, it would be impossible to hear the dead man's heart beating at this late stage.

Does the imagined beating of the dead man's heart, suggesting guilt, make the protagonist sane or insane in "The Tell-Tale Heart"?

If you look at the many different cues in the story you may find three facts about the narrator:

• he (or she, we never know) premeditates and seems to enjoy the killing (joy)
• there is the pain that you mention in some particulars of the killing (sadness)
• the narrator identifies himself as "nervous", "sleepless", and extremely emotional (anxiety)

While these are clear signs of a mentally ill and unstable individual who cannot control his own impulses, this is no ordinary murderer. This is not the typical psychopath or sociopath who is narcissistic and entirely devoid of empathy. This killer does show emotion. This one may be entirely empathetic by nature, but his physical impediments and mental conditions have rendered him unable to abide by his natural gifts. In fact, his brain might have rendered him limited to act like his nature would dictate him to.

It is a typical battle of nature versus nurture; of the body versus the mind. This conflict is particularly painful to the narrator, who is indeed pained by what he did. His entire confession begs for compassion and screams for help. You might as well not typecast the narrator as a typical murderer, but merely as a very crazy and disturbed man who is aware of his unhappy condition. 

Therefore, you are correct in that there is conscience in the man. He loses it, in fact, he loses everything he is about as a result of his mental condition. He knows it, too. He cannot control himself. This is a great touch that Poe adds to make the situation all the more tragic. 

How would you argue for the narrator's innocence due to insanity in The Tell-Tale Heart?

The first thing you need to determine is what events in the story show that the narrator is insane.  One event that might show his insanity is the obsessive nightly visits he makes to the old man’s room with a lantern that shines a ray of light onto the old man’s eye.  The fact that he hallucinates he hears a beating heart under the floorboards is another reason to claim insanity as a defense. 

I would start your essay with your claim and then answer the question, why?

For example, here is a possible thesis--

The narrator in “The Tell Tale Heart” is innocent due to insanity because of his obsessive actions and hallucinations. 

Then back it up with your examples and proof.  Be sure to conclude your essay with a statement that restates your argument’s claim.