[O]nly if every individual strives for truth can humanity attain a happier future; the atavisms in each of us that stand in the way of a friendlier destiny can only thus be rendered ineffective.
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.
Human freedom is realised in the adoption of humanity as an end in itself, for the one thing that no-one can be compelled to do by another is to adopt a particular end. - 'Metaphysical Principles of Virtue
But we have reason to cool our raging motions, our carnal stings, our unbitted lusts; whereof I take this that you call love to bea sect or scion.... It is merely a lust of the blood and a permission of the will.
Man is the will, and woman the sentiment. In this ship of humanity, Will is the rudder, and Sentiment the sail; when woman affects to steer, the rudder is only a masked sail.