The terms good and bad indicate no positive quality in things regarded in themselves, but are merely modes of thinking or notions, which we form from the comparison of things one with another. Thus one and the same thing can be at the same time good, bad, and indifferent. For instance, music is good for him that is melancholy, bad for him that mourns; for him that is deaf; it is neither good nor bad.

The highest activity a human being can attain is learning for understanding, because to understand is to be free.

I would warn you that I do not attribute to nature either beauty or deformity, order or confusion. Only in relation to our imagination can things be called beautiful or ugly, well-ordered or confused.

Nature has no goal in view, and final causes are only human imaginings.

Peace is not the absence of war, but a virtue based on strength of character.

From what has been said we can clearly understand the nature of Love and Hate. Love is nothing else but pleasure accompanied by the idea of an external cause: Hate is nothing else but pain accompanied by the idea of an external cause. We further see, that he who loves necessarily endeavors to have, and to keep present to him, the object of his love; while he who hates endeavors to remove and destroy the object of his hatred.

Love is nothing but joy accompanied with the idea of an eternal cause.