Did Rappaccini love his daughter in "Rappaccini's Daughter"?

Rappaccini comes across as a cold, insensitive man. When Giovanni first sees him tending to his flowers, he observes that the doctor “avoids the actual touch of the flowers, or the direct inhaling of their odors,” almost like he is “walking among malignant influences, such as savage beasts, or deadly snakes, or evil spirits,” instead of beautiful flowers. Thus, when Signor Pietro Baglioni, a Professor of Medicine at the University of Padua, tells him that the doctor Rappaccini “cares more for science than mankind,” and that he has little compassion for other human beings, he is not completely surprised by this information. However, he points out to Baglioni, that from his observations, Rappaccini appears to have great affection for his daughter Beatrice. Baglioni says that it is said that Rappaccini has taught Beatrice all there is to know of his science and that Beatrice is widely known for her beauty. What the two do not know at this point is that Beatrice is as poisonous as the flowers she tends to in the garden. Indeed, as Baglioni himself confesses to Giovanni towards the end of the story, “Rapaccinni was not restrained by natural affection from offering up his child as a victim of his insane zeal for science.” Beatrice’s breath is so poisonous that it causes fresh flowers to wither, and insects and lizards to die.

Having isolated his daughter from all humanity because of his passion for science, Rapaccini seeks to find a companion for Beatrice. This companion is none other than Giovanni, who is himself fed with Rapaccini’s poison until his breath becomes as poisonous as Beatrice’s. When Giovanni learns that he has been caught in Rapaccini’s trap, he says this to Beatrice:

Yes, poisonous thing! Thou hast done it! Thou hast blasted me! Thou hast filled my veins with poison! Thou hast made me as hateful, as ugly, as loathsome, and deadly a creature as thyself – a world’s wonder of hideous monstrosity!

Beatrice, on her part, denies being a part of the plan to turn him into a poisonous being. She says,

It is my father’s fatal science? No, no Giovanni; it was not I! Never, never! I dreamed only to love thee and be with thee a little time, and so to let thee pass away, leaving but thine image in mine heart . . . But my father, he has united us in this fearful sympathy.

By finding a companion for Beatrice, Rapaccini demonstrates a twisted kind of love for his daughter. In fact, Rapaccini seems to think that by making his daughter poisonous he has given her the best gift that a loving father would bequeath his daughter. When his daughter complains of the misery his actions have caused her, he says this:

What mean you, foolish girl? Dost thou deem it misery to be endowed with marvelous gifts, against which no power nor strength could avail an enemy? Misery, to be able to quell the mightiest with a breath? Misery to be as terrible as thou art beautiful? Wouldst thou, then, have preferred the condition of a weak woman, exposed to all evil, and capable of none?

In the end, Rapaccini loses Beatrice, after she drinks the anecdote given to her by Giovanni.

Why did Rappaccini poison his daughter in "Rappaccini's Daughter"?

As Professor Baglioni tells Giovanni, Rappaccini

cares infinitely more for science than for mankind.

Baglioni goes on to say that Rappaccini would sacrifice anyone, even himself or someone he loved, for scientific knowledge. As Baglioni puts it,

He would sacrifice human life, his own among the rest, or whatever else was dearest to him, for the sake of adding so much as a grain of mustard-seed to the great heap of his accumulated knowledge.

It is this cold and obsessive thirst for knowledge that causes Rappaccini to use even his beloved daughter. The scientist researches poisons, and this leads him to poison his daughter so that she can work with, touch, and inhale his deadly poisonous plants without being harmed. However, this leaves her isolated, as her breath kills normal life. Her father, to give her a companion, arranges for Giovanni also to be poisoned so that his breath, too, becomes fatal.

In his madness, Professor Rappaccini believes he has done his daughter a favor in offering her a power that other humans lack. When she accuses him of forcing her to live in misery, he responds,

Misery, to be able to quell the mightiest with a breath? Misery, to be as terrible as thou art beautiful?

Rappaccini projects his own love of knowledge on his daughter, thinking she is as willing as he is to pay any price to advance science. He does not realize that there are limits to what is acceptable in the pursuit of knowledge and power, because, in his singlemindedness, he has completely lost his moral compass. He loves his daughter, but not enough to realize the implications of what he has done to her and that she would prefer to death to sacrificing additional people, like Giovanni, to her father's cause.

Why does Dr. Rappaccini need his daughter's help in "Rappaccini's Daughter"?

In "Rappaccini's Daughter" by Nathaniel Hawthorne, Dr. Giacomo Rappaccini is a classical evil scientist figure, whose towering intellect and intellectual curiosity have led him to delve into the science of poisons and poisonous plants, to the point where is is willing to sacrifice his ethics and family for his studies. The apparently genial Dr. Pietro Baglioni is a rival scientist who may be acting in the story out of benevolence but perhaps out of professional rivalry. 

Dr. Rappaccini's garden is filled with plants so poisonous that no ordinary person can touch them safely. The most dangerous of them all is a shrub with purple blossoms growing by a fountain. Dr. Rappaccini himself can only tend his plants while wearing heavy protective garments, including gloves and sometimes a mask. His daughter, brought up among the plants, has developed an immunity to their poisons, and can can tend them barehanded, albeit at the cost of becoming herself toxic to normal people. Thus Dr. Rappaccini needs his daughter because her immunity to the poisons enables her to tend his experiments.