Immaturity is the incapacity to use one's intelligence without the guidance of another.

Of all the arts poetry (which owes its origin almost entirely to genius and will least be guided by precept or example) maintains the first rank.

In the kingdom of ends everything has either a price or a dignity. Whatever has a price can be replaced by something else as its equivalent; on the other hand, whatever is above all price, and therefore admits of no equivalent, has a dignity. But that which constitutes the condition under which alone something can be an end in itself does not have mere relative worth, i.e., price, but an intrinsic worth, i.e., a dignity.

All the interests of my reason, speculative as well as practical, combine in the three following questions: 1. What can I know? 2. What ought I to do? 3. What may I hope?

Suicide is not abominable because God prohibits it; God prohibits it because it is abominable.

Men will not understand ... that when they fulfil their duties to men, they fulfil thereby God's commandments; that they are consequently always in the service of God, as long as their actions are moral, and that it is absolutely impossible to serve God otherwise.

Act only according to that maxim whereby you can at the same time will that it should become a universal law.