In Shakespeare's Julius Caesar, it is ironic that in Act I Cassius tells Brutus
Men at some time are masters of their fates:
The fault, dear Brutus, is not in our stars,
But in ourselves, that we are underlings. (1.2.145-147)
For, Cassius is at times master of his fate, and at others is himself superstitious and weak.
In Act I, Scene 2, from which these lines come Cassius persuasively convinces Brutus to join the conspiracy to assassinate Caesar. In Act III after the men have slain Caesar, it is Cassius who recognizes the threat that Marc Antony poses; he advises Brutus to have Antony killed. But, Brutus tells him that they will make a friend of Antony. Wisely, Cassius replies that his doubts always turn out to be justified,
I wish we may. But yet have I a mind
That fears him much; and my misgiving still
Falls shrewdly to the purpose. (3.1.158-160)
Then, when Brutus gives Antony permission to address the Romans after he does, Cassius warns him against doing so: "You know not what you do" (3.1.250), His suspicions of Antony are correct, but he defers to Brutus. Still, he expresses his anxiety,
I know not what may fall; I like it not he defers to Brutus. (3.1.262)
Of course, Marc Antony turns against them and becomes their mortal enemy, fomenting a civil war, and defeating them at Philippi. Even there, Cassius's assessments are correct, for he suggests that his and Brutus's troops to remain at Sardis and force the others to advance so that they will be fatugued and use valuable resources, but Brutus disagrees. As it turns out, Cassius again is correct, although he has acquiesced to Brutus.
But, just before this final battle, Brutus and Cassius quarrel bitterly. Cassius accuses Brutus of wronging him repeatedly, and complains weakly that Brutus no longer loves him:
Hath Cassius lived
To be but mirth and laghter to his Brutus
When grief and blood ill-tempered vexeth him? (4.3.124-126)
just as he has been worried in the first act:
Brutus, I do observe you now of late;
I have not from your eyes that gentleness
And show of love as I was wont to have (1.2.36-38)
Finally, Cassius becomes weakly superstitious. In Act 5 he talks to Messala, telling him that even though he "held Epicurus strong" and has not believed in omens, now he has seen
Two mighty eagles fell, and there they perched,
Gorging and feeding from our soldiers' hands,
Who to Philippi here consorted us.
This morning are they fled away and gone,
And in their steads do ravens, crows, and kites
Fly o'er our heads and downward....
Our army lies, ready to give up the ghost. (5.1.87-93)
In the end, Cassius still has wisdom, but he is fearful and superstitious, and defers to Brutus.
One of the triumvirs after the death of Caesar, Lepidus is considered unworthy to be one of the three rulers of the Roman empire by Marc Antony, while, on the other hand, Octavius is willing to honor him as "a tried and valiant soldier" (4.1.32). At the beginning of Act IV, the triumvirate compile a death list of their political enemies. Lepidus is sent to get Caesar's will so they can reduce some of the legacies in it; when he returns, with a lack of honor, Lepidus consents to allow his brother to die provided Antony will sacrifice his nephew. So, while he may be an excellent soldier, Lepidus lacks loyalty to his family.
In Shakespeare's play, Julius Caesar, Cassius is able to scheme and manipulate, and is a good judge of character. This might be considered a strength as he is able to convince people to do what he wants. However, he is weak in that his motivation is based mostly on self-interest and jealousy.
In Act I, scene ii, Cassius tries to convince Brutus to turn against Caesar and become a part of the plot against him, as seen in this, the "seduction scene:"
Brutus, and Caesar: what should be in that Caesar?
Why should that name be sounded more than yours?
Write them together, yours is as fair a name;
Sound them, it doth become the mouth as well... (I, ii, 148-151)
Here Cassius is telling Brutus that he is just as good as Caesar; why should people call out Caesar's name more than Brutus' as they are both equally as good. In this quote we can see that Cassius is a good judge of character, as he would never have approached Brutus if he thought the plot would be betrayed by the man.
The following quote exemplifies Cassius' jealousy...
Caesar cried, “Help me, Cassius, or I sink!”
I, as Aeneas our great ancestor
Did from the flames of Troy upon his shoulder
The old Anchises bear, so from the waves of Tiber(120)
Did I the tired Caesar. And this man
Is now become a god, and Cassius is
A wretched creature, and must bend his body
If Caesar carelessly but nod on him. (I, ii, 117-124)
In this quote Cassius recalls Caesar calling for him when he was drowning in the Tiber River, and Cassius carried him out and saved him. Now, Cassius laments, Caesar has become like a god, and Cassius is nothing but a "wretched creature," who has to bow if Caesar (who owes his life to Cassius) casually nods at him.
After Caesar's death, Lepidus is a triumvir (one of three rulers). Whereas Octavius wants to honor his service as a soldier, Antony does not believe Lepidus is good enough to be one of three rulers of Rome.
In terms of his weaknesses, Lepidus is an old man; he has very little power even though he is one of the leaders of the Roman Empire. He "lacks worldly wisdom," but, as Octavious points out, he is loyal and was a brave soldier.
Antony shares his feelings regarding Lepidus in the following passage:
This is a slight unmeritable man,
Meet to be sent on errands. Is it fit,
The three-fold world divided, he should stand
One of the three to share it? (IV, i, 13-16)
Antony questions the legitimacy of Lepidus' important role in the government when he is really only good for running errands.
Octavius defends the old man, Lepidus:
You may do your will,
But he's a tried and valiant soldier. (IV, i, 30-31)
Having known Lepidus for a long time, Octavius notes that he is a brave soldier with a great deal of experience on the battlefield. He points out that Antony thought better of Lepidus when it suited him.
As with all people, each has strengths and weaknesses. It would seem that Lepidus is the more honorable man, and Cassius less honorable and more self-interested.