When I could have used a wife, I could not support one; and when I could support one, I no longer needed any

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

The yellow Indians do have a meagre talent. The Negroes are far below them, and at the lowest point are a part of the American people.

It is difficult for the isolated individual to work himself out of the immaturity which has become almost natural for him.

Our knowledge springs from two fundamental sources of the mind; the first is the capacity of receiving representations (receptivity for impressions), the second is the power of knowing an object through these representations (spontaneity [in the production] of concepts).

It is often necessary to make a decision on the basis of knowledge sufficient for action but insufficient to satisfy the intellect.

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.