All Leading to Dark Passages

John Keats, letter to John Hamilton Reynolds (May 3rd, 1818), Letters of John Keats to his Family and Friends, ed. Sidney Colvin (London: Macmillan and Co., 1891), p. 107-108:

I compare human life to a large Mansion of Many apartments, two of which I can only describe, the doors of the rest being as yet shut upon me — The first we step into we call the infant or thoughtless Chamber, in which we remain as long as we do not think — We remain there a long while, and notwithstanding the doors of the second Chamber remain wide open, showing a bright appearance, we care not to hasten to it; but are at length imperceptibly impelled by the awakening of the thinking principle within us we no sooner get into the second Chamber, which I shall call the Chamber of Maiden-Thought, than we become intoxicated with the light and the atmosphere, we see nothing but pleasant wonders, and think of delaying there for ever in delight: However among the effects this breathing is father of is that tremendous one of sharpening one's vision into the heart and nature of Man — of convincing one's nerves that the world is full of Misery and Heartbreak, Pain, Sickness, and oppression — whereby this Chamber of Maiden Thought becomes gradually darkened, and at the same time, on all sides of it, many doors are set open — but all dark — all leading to dark passages — We see not the balance of good and evil — we are in a mist — we are now in that state — We feel the "burden of the Mystery."