I think Thus there is no rational psychology as doctrine that might provide us with an addition to our self consciousness, but only as discipline, setting impassable boundaries for speculative reason in this field, in order, on the one side, not to be thrown into the lap of a soulless mate rialism, or on the other side not to get lost wandering about in a spiri tualism that must be groundless for us in life; on the contrary, it rather reminds us to regard this refusal of our reason to give an answer to those curious questions, which reach beyond this life, as reason's hint that we should turn our self knowledge away from fruitless and extrav agant speculation toward fruitful practical uses, which, even if it is al ways directed only to objects of experience, takes its principlesc from for sich Selbsterkenntnis Principien