VI. Our Knowledge of the World

This thought conflicts with a common prejudice which is very hard to overcome. The victims of this prejudice are unable to see that the concept of a triangle which my mind grasps is the same as the concept which my neighbour's mind grasps. The naïve man believes himself to be the creator of his concepts. Hence he believes that each person has his private concepts. One of the first things which philosophic thought requires of us is to overcome this prejudice. The one single concept of “triangle” does not split up into many concepts because it is thought by many minds. For the thought of the many is itself a unity.