Thought gathers, further, from the history of ethics that the latter cannot be conceived as being merely a natural happening which continues itself in man. In the ethical man natural happenings come into contradiction with themselves. Nature knows only a blind affirmation of life. The will-to-live which animates natural forces and living beings is concerned to work itself out unhindered. But in man this natural effort is in a state of tension with a mysterious effort of a different kind. Life-affirmation exerts itself to take up life-denial into itself in order to serve other living beings by self-devotion, and to protect them, even eventually by self-sacrifice, from injury or destruction. It is true that self-devotion plays a certain _rôle_ in non-human living beings. As a temporary instinct it rules in sexual love and in parental love; as a permanent instinct it is found in certain individual members of animal species (_e.g._, ants, bees) which, because sexless, are incomplete individualities. These manifestations are in a certain way a prelude to the interplay of life-affirmation and life-denial which is at work in the ethical man. They do not, however, explain it. That which is active elsewhere only as a temporary instinct, or as an instinct in incomplete individualities and that, too, always within special relations of solidarity with others, becomes now, in man, a steady, voluntary, unlimited form of action, a result of thought, in which individuals endeavour to realise the higher life-affirmation. How does this come about? Here one is faced once more by the problem of the _rôle_ which thought plays in the origin of ethics. It seizes on something of which a preliminary form is seen in an instinct, in order to extend it and bring it to perfection. It comprehends the content of an instinct, and tries to give it practical application in new and consistent action. [pg 227] In some way or other the _rôle_ of thought lies in the fulfilment of life-affirmation. It rouses the will-to-live to recognise as in analogy with the life-affirmation which is in itself, the life-affirmation which shows itself in the manifold life which is everywhere around it, and to join in its experiences. On the foundation of this world-affirmation life-denial takes its place as a means of helping forward this affirmation of other life than its own. It is not life-denial in itself that is ethical, but only such as stands in the service of world-affirmation and becomes purposive within it. Ethics are a mysterious chord in which life-affirmation and world-affirmation are the ground-note and the fifth; life-denial is the third.