Question

he who gives himself entirely to his fellow men; which of these rhetorical devices does thoreua use here?A.theme B.simile C.metaphor D.parallelism

Answer 1

It's not parallelism. The idea is not repeated in a slightly different way.

It's not a simile or metaphor. Compared to what? The sentence is a fragment.

That only leaves A but it's not a good answer. The sentence is incomplete.

Did you leave something out?

If you had 
He who gives to himself entirely to his fellow man, gives entirely to himself.
That would be parallel.

Answer 2

Answer:

D. Parallelism.

Explanation:

Parallelism is a rhetoric device used in writing to create a harmonious effect.  It is the repetition of grammatical elements that are same either in their construction, meaning, sound or meter.

Henry David Thoreau was an American essayist, philosopher and poet.

In his essay, "Civil Disobedience" or "Resistance to Civil Government", he talks about that the people should not allow government to overrule their conscience. In his views, the government instead of being just is an agent of corruption and injustice.

In his speech, he says,

"He who gives himself entirely to his fellow-men appears to them useless and selfish; but he who gives himself partially to them is pronounced a benefactor and philanthropist.(66-67)"

The rhetorical device that Thoreau had used in this part of his speech is  Parallelism.