“It is the glistening and softly spoken lie; the amiable fallacy; the patriotic lie of the historian, the provident lie of the politician, the zealous lie of the partisan, the merciful lie of the friend, and the careless lie of each man to himself, that cast that black mystery over humanity, through which we thank any man who pierces, as we would thank one who dug a well in a desert.”

Section 70
The Passionate State Of Mind, and Other Aphorisms (1955)

Source: It (1986)

Science and Immortality (1904)
Context: The search of science for the spirits has been neither long nor earnest; nor is it a matter of surprise that it has not been undertaken earlier by men whose training had fitted them for the work.
It is no clear, vasty deep, but a muddy, Acheronian pool in which our modern spirits dwell, with Circe as the presiding deity and the Witch of Endor as her high priestess. Commingling with the solemn incantations of the devotees who throng the banks, one can hear the mocking laughter of Puck and of Ariel, as they play among the sedges and sing the monotonous refrain, "What fools these mortals be!" Sadly besmirched, and more fitted for a sojourn in Ancyra than in Athens, has been the condition of those who have returned from the quest, and we cannot wonder that scientific men have hesitated to stir the pool and risk a touch from Circe's wand. All the more honour to those who have with honest effort striven to pierce the veil and explore the mysteries which lie behind it.

Source: Les Misérables

Pablo Picasso said something very similar. Perhaps it is the source? From Herschel B. Chipp’s Theories of Modern Art: "We all know that Art is not truth. Art is a lie that makes us realize truth, at least the truth that is given us to understand."
Disputed

Source: The Judges

Bigger and Blacker (HBO, 1999)

Of Truth
Essays (1625)