A good painter has two main objects to paint, man and the intention of his soul. The former is easy, the latter hard as he has to represent it by the attitude and movement of the limbs.

He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast.

If you are alone you belong entirely to yourself. If you are accompanied by even one companion you belong only half to yourself or even less in proportion to the thoughtlessness of his conduct and if you have more than one companion you will fall more deeply into the same plight.

Therefore, O students, study mathematics and do not build without foundations.

One day the world will look upon research upon animals as it now looks upon research on human beings.

While you are alone you are entirely your own master and if you have one companion you are but half your own, and the less so in proportion to the indiscretion of his behavior.

The cat is nature's masterpiece.