Nietzsche spells this point out in the case of punishment. The act of punishing has always been the same, but the meaning of that act has changed radically. The barbarians of ancient time had very different wills than the modern slave morality endorses. As a result, though the act of punishing and the word "punishment" have remained unchanged, they have been interpreted very differently. Nietzsche is showing that what is significant to us about punishment is not the act itself, but the meaning that we attach to it. Because this meaning is independent of and inessential to the act itself, we could potentially come to understand punishment as meaning pretty much anything. Because conventional wisdom sees the world in terms of things and deeds rather than forces and wills, we are unable to separate the meanings of punishment from the deed itself, and assume that the deed has always had the same meaning. Nietzsche raises the same point with pretty much all our moral concepts, showing that, while the words "good," "conscience," "guilt," or "justice" have been around for a long time, they have, unnoticed by us, taken on very different meanings depending on the wills that were interpreting them.