Generally, people, they indulge in mental speculation. Different philosophy of the world, they are established on the principle of mental speculation, especially in Europe, Aristotle, Schopenhauer, Kant. They're more or less... And, imitating the Western philosophers, in India also, recently, the persons who are very well known... Perhaps you know Sri Aurobindo. He's, he's also speculated very nicely on the mental platform. Mental platform cannot give us the actual freedom or the happiness. Therefore Lord says, "One should give up all mental speculation and should be satisfied in the understanding that 'I am consciousness, and there is Supreme Consciousness, and I am subordinate to the Supreme Consciousness. Therefore let me dovetail my consciousness with the Supreme Consciousness.' "
Lecture on Bhagavad-gita 2.55-58, New York, April 15, 1966