104 Self Defence.—If self defence is in general held a valid justification, then nearly every manifestation of so called immoral egoism must be justified, too. Pain is inflicted, robbery or killing done in order to maintain life or to protect oneself and ward off harm. A man lies when cunning and delusion are valid means of self preservation. To injure intentionally when our safety and our existence are involved, or the continuance of our well being, is conceded to be moral. The state itself injures from this motive when it hangs criminals. In unintentional injury the immoral, of course, can not be present, as accident alone is involved. But is there any sort of intentional injury in which our existence and the maintenance of our well being be not involved? Is there such a thing as injuring from absolute badness, for example, in the case of cruelty? If a man does not know what pain an act occasions, that act is not one of wickedness. Thus the child is not bad to the animal, not evil. It disturbs and rends it as if it were one of its playthings. Does a man ever fully know how much pain an act may cause another? As far as our nervous system extends, we shield ourselves from pain. If it extended further, that is, to our fellow men, we would never cause anyone else any pain (except in such cases as we cause it to ourselves, when we cut ourselves, surgically, to heal our ills, or strive and trouble ourselves to gain health). We conclude from analogy that something pains somebody and can in consequence, through recollection and the power of imagination, feel pain also. But what a difference there always is between the tooth ache and the pain (sympathy) that the spectacle of tooth ache occasions! Therefore when injury is inflicted from so called badness the degree of pain thereby experienced is always unknown to us: in so far, however, as pleasure is felt in the act (a sense of one’s own power, of one’s own excitation) the act is committed to maintain the well being of the individual and hence comes under the purview of self defence and lying for self preservation. Without pleasure, there is no life; the struggle for pleasure is the struggle for life. Whether the individual shall carry on this struggle in such a way that he be called good or in such a way that he be called bad is something that the standard and the capacity of his own intellect must determine for him.
From Human, All Too Human by Friedrich Nietzsche