Provocative passage from Nietzsche, Human, all too Human:

For this reason a higher culture must give to man a double-brain, as it were two brain ventricles, one for the perceptions of science, the other for those of non-science: lying beside one another, not confused together, separable, capable of being shut off; this is the demand of health. In one domain lies the power-source, in the other the regulator: it must be heated with illusions, onesidedness, passions, the evil and perilous consequences of overheating must be obviated with the aid of the knowledge furnished by science. – If this demand of higher culture is not met, then the future course of human evolution can be foretold almost with certainty: interest in truth will cease the less pleasure it gives: because they are associated with pleasure, illusion, error and fantasy will regain step by step the ground they formerly held: the ruination of science, a sinking back into barbarism, will be the immediate consequence; mankind will have to begin again at the weaving of its tapestry, after having, like Penelope, unwoven it at night. (HH1, 251)