are born to create, the second to investigate. The difference between them is like that between a spendthrift and a miser, between exhaling and inhaling. It is difficult to tell which is the better: the first have the gift of creating; the second of developing, and above all of digesting. In the second this is active; true, the stomach has that power also. A perfect balance between these powers constitutes genius. In such a case there is a natural need of broad movements.

Yosef had the second capacity, the classifying. He not only had it, but he knew that he had it; this conviction preserved him in life from many mistakes, and gave a certain balance to his wishes and capacities. He never undertook a thing that for him was impossible. He calculated with himself. And, finally, he had much enthusiasm, which in his case might have been called persistence in science. Having a mind which was fond of examining everything soberly, he wanted to see everything well; but to see well one must know thoroughly. He was unable to guess, he wished to know.

This was why he never learned anything half-way. As a spider surrounds a fly, he surrounded his subject of investigation diligently