“Things which as effects presuppose others as causes cannot be reciprocally at the same time causes of these.”

Freedom, is a property of all rational beings.

Nature is beautiful because it looks like Art; and Art can only be called beautiful if we are conscious of it as Art while yet it looks like Nature.

The enjoyment of power inevitably corrupts the judgement of reason, and perverts its liberty.

Morality is not properly the doctrine of how we may make ourselves happy, but how we may make ourselves worthy of happiness.

Woman wants control, man self-control.

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.

The great mass of people are worthy of our respect.

Laughter is an affect resulting from the sudden transformation of a heightened expectation into nothing.

The greatest human quest is to know what one must do in order to become a human being.

Prudence reproaches; conscience accuses.

From such crooked wood as that which man is made of, nothing straight can be fashioned.

Dare to know! Have the courage to use your own intelligence!

Space and time are the framework within which the mind is constrained to construct its experience of reality.

Settle, for sure and universally, what conduct will promote the happiness of a rational being.

All our knowledge begins with the senses, proceeds then to the understanding, and ends with reason. There is nothing higher than reason.

Since the human race’s natural end is to make steady cultural progress, its moral end is to be conceived as progressing toward the better. And this progress may well be occasionally interrupted, but it will never be broken off.

To make a contented slave it is necessary to make a thoughtless one. It is necessary to darken the moral and mental vision and, as far as possible, to annihilate the power of reason.

The very essence of instinct is that it’s followed independently of reason.

The soul of man is divided into three parts, intelligence, reason, and passion. Intelligence and passion are possessed by other animals, but reason by man alone.

My pain may be the reason for somebody’s laugh. But my laugh must never be the reason for somebody’s pain.

I call him free who is led solely by reason.

He alone is free who lives with free consent under the entire guidance of reason.

It is hard enough to remember my opinions, without also remembering my reasons for them!

The grand thing is to be able to reason backwards.