Our biological essence, our instinct remnants, are weak and subtle, and they are hard to get at. Learnings of the extrinsic sort are more powerful than our deepest impulses. These deepest impulses in the human species, at the points where the instincts have been lost almost entirely, where they are extremely weak, extremely subtle and delicate, where you have to dig to find them, this is where I speak of introspective biology, of biological phenomenology, implying that one of the necessary methods in the search for self, the search for spontaneity and for naturalness is a matter of closing your eyes, cutting down the noise, turning off the thoughts, putting away all busyness, just relaxing in a kind of Taoistic and receptive fashion.

— Abraham Maslow, Farther Reaches of Human Nature