I believe the word that best describes the tone of the passage is:
3. philosophical.
Explanation:
The passage is questioning the very nature of man - our capacity to be both good and evil, vile and noble. The beginning of the passage itself presents a philosophical question: "Was man, indeed, at once so powerful, so virtuous and magnificent yet so vicious and base?" Philosophy has as its purpose the questioning of our assumptions and understandings concerning different topics - for instance life, morals, behavior, meanings, etc. A passage that questions human nature seems, therefore, to be a philosophical passage.
