An imaginative life may therefore exist parasitically in a man, hardly touching his action or environment. There is no possibility of exorcising these apparitions by their own power. A nightmare does not dispel itself; it endures until the organic strain which caused it is relaxed either by natural exhaustion or by some external influence. Therefore human ideas are still for the most part sensuous and trivial, shifting with the chance currents of the brain, and representing nothing, so to speak, but personal temperature. Personal temperature, moreover, is sometimes tropical. There are brains like a South American jungle, as there are others like an Arabian desert, strewn with nothing but bones. While a passionate sultriness prevails in the mind there is no end to its luxuriance. Languages intricately articulate, flaming mythologies, metaphysical perspectives lost in infinity, arise in remarkable profusion. In time, however, there comes a change of climate and the whole forest disappears. It is easy, from the stand-point of acquired practical competence, to deride a merely imaginative life. Derision, however, is not interpretation, and the better method of overcoming erratic ideas is to trace them out dialectically and see if they will not recognise their own fatuity. The most irresponsible vision has certain principles of order and valuation by which it estimates itself; and in these principles the Life of Reason is already broached, however halting may be its development. We should lead ourselves out of our dream, as the Israelites were led out of Egypt, by the promise and eloquence of that dream itself. Otherwise we might kill the goose that lays the golden egg, and by proscribing imagination abolish science. [Sidenote: Intrinsic pleasure in existence.] [Sidenote: Pleasure a good,]