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

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

Nothing is divine but what is agreeable to reason.

Philosophical knowledge is the knowledge gained by reason from concepts ; mathematical knowledge is the knowledge gained by reason from the construction of concepts.

cruelty to animals is contrary to man's duty to himself, because it deadens in him the feeling of sympathy for their sufferings, and thus a natural tendency that is very useful to morality in relation to other human beings is weakened.

If, like Hume, I had all manner of adornment in my power, I would still have reservations about using them. It is true that some readers will be scared off by dryness. But isn't it necessary to scare off some if in their case the matter would end up in bad hands?