It is no doubt more difficult to characterise these active forces for, by nature, they escape consciousness, "The great activity is unconscious". Consciousness merely expresses the relation of certain reactive forces to the active forces which dominate them. Consciousness is essentially reactive; this is why we do not know what a body can do, or what activity it is capable of. And what is said of consciousness must also be said of memory and habit. Furthermore we must also say it of nutrition, reproduction, conservation and adaptation. These are reactive functions, reactive specialisations, expressions of particular reactive forces. It is inevitable that consciousness sees the organism from its own point of view and understands it in its own way; that is to say, reactively . What happens is that science follows the paths of consciousness, relying entirely on other reactive forces; the organism is always seen from the petty side , from the side of its reactions. The problem of the organism, according to Nietzsche, is not an issue between mechanism and vitalism. What is the value of vitalism as long as it claims to discover the specificity of life in the same reactive forces that mechanism interprets in another way? The real problem is the discovery of active forces without which the reactions themselves would not be forces.
Deleuze on Nietzsche // The book