Act in such a way that you treat humanity, whether in your own person or in the person of any other, never merely as a means to an end, but always at the same time as an end.

An organized product of nature is that in which all the parts are mutually ends and means.

In the mere concept of one thing it cannot be found any character of its existence.

We find that the more a cultivated reason devotes itself to the aim of enjoying life and happiness, the further does man get away from true contentment.

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

The instruction of children should aim gradually to combine knowing and doing. Among all sciences mathematics seems to be the only one of a kind to satisfy this aim most completely.

We ourselves introduce that order and regularity in the appearance which we entitle "nature". We could never find them in appearances had we not ourselves, by the nature of our own mind, originally set them there.