Scientific truth is universal, because it is only discovered by the human brain and not made by it, as art is.

All scientific knowledge to which man owes his role as master of the world arose from playful activities.

Hatred of humanity and love of animals make a very bad combination.

The scientist knows very well that he is approaching ultimate truth only in an asymptotic curve and is barred from ever reaching it; but at the same time he is proudly aware of being indeed able to determine whether a statement is a nearer or a less near approach to the truth.

If you confine yourself to this Skinnerian technique, you study nothing but the learning apparatus and you leave out everything that is different in octopi, crustaceans, insects and vertebrates. In other words, you leave out everything that makes a pigeon a pigeon, a rat a rat, a man a man, and, above all, a healthy man healthy and a sick man sick.

We had better dispense with the personification of evil, because it leads, all too easily, to the most dangerous kind of war: religious war.

The human soul is very much older than the human mind.