Reason must approach nature in order to be taught by it. It must not, however, do so in the character of a pupil who listens to everything that the t….

The means employed by Nature to bring about the development of all the capacities of men is their antagonism in society, so far as this is, in the en….

In the metaphysical elements of aesthetics the various nonmoral feelings are to be made use of; in the elements of moral metaphysics the various mora….

Marriage...is the union of two people of different sexes with a view to the mutual possession of each other's sexual attributes for the duration of t….

Reason in a creature is a faculty of widening the rules and purposes of the use of all its powers far beyond natural instinct; it acknowledges no lim….

The greatest problem for the human species, the solution of which nature compels him to seek, is that of attaining a civil society which can administ….

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

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

The only objects of practical reason are therefore those of good and evil. For by the former is meant an object necessarily desired according to a pr….

If an offender has committed murder, he must die. In this case, no possible substitute can satisfy justice. For there is no parallel between death an….

A society that is not willing to demand a life of somebody who has taken somebody else’s life is simply immoral..

Life is the faculty of spontaneous activity, the awareness that we have powers..

A science of all these possible kinds of space [the higher dimensional ones] would undoubtedly be the highest enterprise which a finite understanding….

The possession of power inevitably spoils the free use of reason..

The inscrutable wisdom through which we exist is not less worthy of veneration in respect to what it denies us than in respect to what it has granted..

The desire which a man has for a woman is not directed towards her because she is a human being, but because she is a woman ; that she is a human bei….

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

If justice perishes, human life on Earth has lost its meaning..

The evil effect of science upon men is principally this, that by far the greatest number of those who wish to display a knowledge of it accomplish no….

Act that your principle of action might safely be made a law for the whole world..

Democracy is necessarily despotism, as it establishes an executive power contrary to the general will; all being able to decide against one whose opi….