If man makes himself a worm he must not complain when he is trodden on.

In law a man is guilty when he violates the rights of others. In ethics he is guilty if he only thinks of doing so.

[R]eason is... given to us as a practical faculty, that is, as one that influences the will.

Two things fill the mind with ever-increasing wonder and awe, the more often and the more intensely the mind of thought is drawn to them: the starry heavens above me and the moral law within me... Morality is not properly the doctrine of how we may make ourselves happy, but how we may make ourselves worthy of happiness.

Animals... are there merely as a means to an end. That end is man.

A categorical imperative would be one which represented an action as objectively necessary in itself, without reference to any other purpose.

The greatest human quest is to know what one must do in order to become a human being.