From C.S. Lewis, The Abolition of Man:
From this point of view the conquest of nature appears in a new light. We reduce things to mere Nature in order that we may ‘conquer’ them. We are always conquering Nature, because ‘Nature’ is the name for what we have, to some extent, conquered. The price of conquest is to treat thing as mere Nature. Every conquest over Nature increases her domain. The stars do not become Nature till we can weigh and measure them: the soul does not become Nature until we can psycho-analyze her. The wresting of powers from nature is also the surrendering of things to nature. As long as this process stops short of the final stage we may well hold that the gain outweighs the loss. But as soon as we take the final step of reducing our own species to the level of Nature, the whole process is stultified, for this time the being who stood to gain and the being who has been sacrificed are one and the same…. It is in Man’s power to treat himself as a mere ‘natural object’ and his own judgements of value as raw material for scientific manipulation to alter at will. The objection to his doing so does not lie in the fact that his point of view (like one’s first day in a dissecting room) is painful and shocking till we grow used to it. The pain and shock are at most a warning and a symptom. The real objection is that it if man choose to treat himself as raw material, raw material he will be.