Like most other subjects under discussion today, the theory of nature is largely controlled by considerations of knowledge. Treatment of it is, consequently, incidental to the treatment of these other problems, and is undertaken, in the main, because they compel it. A brief catalogue of characteristic statements about nature will illustrate this. “Nature,” says one writer, “is that which we observe in perception through the senses”; and another writes, “It is not experience which is experienced, but nature—stones, plants, animals, diseases, health, temperature, electricity, and so on.” Nothing is more apparent in these sentences than the fact that it is not nature that the writers are so much concerned with, as with what it is that appears through the senses. The theory of nature, that is, is not so much guided by an analysis of the word's context and usage, as it is by the question: what is the proper object of knowledge? Consequently it is the latter question that is answered and not the question: what is nature? The reason for this is evident in the purpose of these statements and in their history; their purpose: the desire to do away with the separation between experience and nature, and to transform nature into a field familiar and accessible; and their history: the very framework against which they are directed, for they are embedded in the set-up from which they are trying to disentangle themselves. Perhaps something ought to be said to substantiate the thesis that the sentences cited are controlled by the problem of knowledge, especially since their intent seems to be to escape that problem. In any case, their history should serve to clarify them, and render a different approach to the theory of nature more significant.