"Heresy” is dissent or deviation from the accepted norm, especially in a religious sense.

A “quagmire” is a swamp or a conundrum or tricky situation. The swamp is used as a metaphor for a problem or challenge for which one gets "mired in."

An ”antidote” is a remedy that reverses the effects of a poison or venom.

The key to this question is the participial phrase "removing much of the wonder." The implication is that modernity made the world appear "bleak" like equations of physics. By stripping it of its wonder, it made it quite plain and without poetic meaning—at least the sentence claims this. This is not necessarily to destroy the world, and it does not make much sense to say that it depressed the world. (Perhaps it depressed the people.) The word "disenchanted" (or "disenchantment") can be used merely to describe a person who has become disillusioned or has lost interests. It can also describe, in an extended sense, the thing that was disenchanted—the world, which had lost its appearance of being wonderful.

The general idea of this sentence is that the given plan or idea "looked good on paper," though it did not make much sense when you actually tried to do it. Now, this does not mean it is on physical paper. (Hence, "textbook" is not necessarily called for.) What we mean is that "taken in consideration that ignores the details of reality's facts" the idea seemed excellent. Such consideration is made "in the abstract" (as opposed to the concrete). The word "tractor" comes from a similar Latin base meaning "to pull". To "ab"+"stract" is to "pull away from [the details]". The prefix "ab-" means, of course, "away from" (e.g. "absent").

A “raconteur” is a narrator or storyteller.

From the context of the sentence it is apparent that Plato’s work changed the direction of Western thought; therefore the answer we select must reinforce this meaning. Virulence and maliciousness both relate to the bitterness or immorality of an action, as the sentence makes no mention of these concepts we can eliminate these answer choices. Debacle means disaster, which neither fits grammatically nor matches the meaning of the sentence. Perdition means everlasting punishment or hell, which likewise fails in both respects. Only profundity which means intellectual complexity or insight supports the framework of the sentence.

An orator is someone who is talented at speaking to audiences. It stands to reason that the ability to make oneself best understood would be of critical importance to an orator. Articulation, which refers to the coherent expression of thoughts, ideas and narrative, is the best fit for this sentence. Overabundance means to have too much of something. Experiments would be of more useful study to a scientist than an orator. Advancements likewise might be useful for an orator, but far less important than speaking ability. Implementation means to carry out an idea.

From the language of the second clause you know that the blank in the first clause must relate to the oratorical skills of Henry Clay and his ability to argue with great clarity. Orator, if you do not know what it means, is someone who is good at public speaking. Of the five answer choices only rhetoric could be correct. Rhetoric means persuasive speech that communicates a point. Boorishness refers to someone who is ill-mannered; smugness means cockiness; animosity refers to hostility between two or more parties; generosity refers to kindness and selflessness.

The "penumbra" cast by an object is the outer part of its shadow. The word comes from the Latin “umbra,” which means shade or even ghost, as well as from the verb “umbrare,” meaning, to cast a shadow on or to shade. Related words in English are not only “umbrella” and “umbrage” but also “somber” and “sombrero” (really as a Spanish import, of course).