There are three kinds of brains: One understands of itself, another can be taught to understand, and the third can neither understand to itself or be taught to understand.
Anything that is secret and mysterious in this system of Yoga should be at once rejected. The best guide in life is strength. In spirituality, as in all other matters, discard everything that weakens you. Have nothing to do with it. Mystery-mongering weakens the human brain. It has well-nigh destroyed Yoga, one of the grandest of sciences
In every idea of genius or in every new human idea, or, more simply still, in every serious human idea born in anyone's brain, there is something that cannot possibly be conveyed to others.
In order to explain why the ordinary Sadhus and Yogis take to tobacco and gānja [an intoxicant], I said that these cause stimulation of the physical brain. But these have reactions. And to stimulate the brain thus is not the proper process.
Science, already oppressive with its shocking revelations, will perhaps be the ultimate exterminator of our human species - if separate species we be - for its reserve of unguessed horrors could never be borne by mortal brains if loossed upon the world.