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.

The light dove, cleaving the air in her free flight, and feeling its resistance, might imagine that its flight would be still easier in empty space.

Things which we see are not by themselves what we see ... It remains completely unknown to us what the objects may be by themselves and apart from the receptivity of our senses. We know nothing but our manner of perceiving them.

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

All our knowledge begins with the senses...

The question is not so much whether there is life on Mars as whether it will continue to be possible to live on Earth

A lie is the abandonment and, as it were, the annihilation of the dignity by man.