How does art reflect the ideas and events of the Age of Enlightenment and the Democratic Revolutions in the period 1750-1900?

Why is it useful for historians to base certain studies on the analysis of historical periods

What word best describes the tone of this excerpt from "the fall of the house of usher" by edgar allan poe? i looked upon the scene before me—upon the mere house, and the simple landscape features of the domain—upon the bleak walls—upon the vacant eye-like windows—upon a few rank sedges—and upon a few white trunks of decayed trees—with an utter depression of soul which i can compare to no earthly sensation more properly than to the after-dream of the reveller upon opium—the bitter lapse into everyday life—the hideous dropping off of the veil. there was an iciness, a sinking, a sickening of the heart—an unredeemed dreariness of thought which no goading of the imagination could torture into aught of the sublime. what was it—i paused to think—what was it that so unnerved me in the contemplation of the house of usher? it was a mystery all insoluble; nor could i grapple with the shadowy fancies that crowded upon me as i pondered. i was forced to fall back upon the unsatisfactory conclusion, that while, beyond doubt, there are combinations of very simple natural objects which have the power of thus affecting us, still the analysis of this power lies among considerations beyond our depth. it was possible, i reflected, that a mere different arrangement of the particulars of the scene, of the details of the picture, would be sufficient to modify, or perhaps to annihilate its capacity for sorrowful impression; and, acting upon this idea, i reined my horse to the precipitous brink of a black and lurid tarn that lay in unruffled lustre by the dwelling, and gazed down—but with a shudder even more thrilling than before—upon the remodelled and inverted images of the gray sedge, and the ghastly tree-stems, and the vacant and eye-like windows. admiration terror hope discovery loss

Why is it important that dr. luther king jr. use non-violent protest to create social change?