It is strange that this should be the effect of the intellect, for after all it was given only as an aid to the most unfortunate, most delicate, most evanescent beings in order to hold them for a minute in existence, from which otherwise, without this gift, they would have every reason to flee as quickly as Lessing's son. [In a famous letter to Johann Joachim Eschenburg (December 31, 1778), Lessing relates the death of his infant son, who "understood the world so well that he left it at the first opportunity."] That haughtiness which goes with knowledge and feeling, which shrouds the eyes and senses of man in a blinding fog, therefore deceives him about the value of existence by carrying in itself the most flattering evaluation of knowledge itself. Its most universal effect is deception; but even its most particular effects have something of the same character.- Nietzsche, "On Truth and Lies in an Extra-Moral Sense"
The intellect, as a means for the preservation of the individual, unfolds its chief powers in simulation; for this is the means by which the weaker, less robust individuals preserve themselves, since they are denied the chance of waging the struggle for existence with horns or the fangs of beasts of prey. In man this art of simulation reaches its peak: here deception, flattering, lying and cheating, talking behind the back, posing, living in borrowed splendor, being masked, the disguise of convention, acting a role before others and before oneself—in short, the constant fluttering around the single flame of vanity is so much the rule and the law that almost nothing is more incomprehensible than how an honest and pure urge for truth could make its appearance among men. They are deeply immersed in illusions and dream images; their eye glides only over the surface of things and sees "forms"; their feeling nowhere lead into truth, but contents itself with the reception of stimuli, playing, as it were, a game of blindman's buff on the backs of things. Moreover, man permits himself to be lied to at night, his life long, when he dreams, and his moral sense never even tries to prevent this—although men have been said to have overcome snoring by sheer will power.
What, indeed, does man know of himself! Can he even once perceive himself completely, laid out as if in an illuminated glass case? Does not nature keep much the most from him, even about his body, to spellbind and confine him in a proud, deceptive consciousness, far from the coils of the intestines, the quick current of the blood stream, and the involved tremors of the fibers? She threw away the key; and woe to the calamitous curiosity which might peer just once through a crack in the chamber of consciousness and look down, and sense that man rests upon the merciless, the greedy, the insatiable, the murderous, in the indifference of his ignorance—hanging in dreams, as it were, upon the back of a tiger. In view of this, whence in all the world comes the urge for truth?