The stimulus, in these cases, is simply "that phase of activity requiring to be defined in order that a coordination may be completed."[122] It is not any particular existence, and is not to be taken as an element apart from others, having an independent existence. But the conscious process of attending to the sensation and finding a response to it arises only when coordination is disturbed by conflicting factors, and the separation of stimulus from response arises only as a means for bringing unity into the coordination. The sensation, then, is that element which is to be attended to; upon which further response depends. This phase of the teleological interpretation defines each element by the part which it plays in the reflective process. If this brief summary of the article is difficult to comprehend, a reading of the original text will do little towards making it more intelligible. The doctrine presented there, however, is simple and coherent enough when its bearings and purpose are once understood, and, at the risk of being over-elaborate, it seems advisable to attempt some remarks on the general bearing and applications of the theory. It must be remembered that Dewey is seeking an interpretation of the thought process which shall reveal it as an actual fact of experience. A thought which is apart from experience and not _in_ it, which is shut up to the contemplation of its own mental states is, by its definition, non-experienced. It is, like Kant's 'productive imagination,' formative of experience, but not a part of it. Dewey holds to the belief that experience must be explained in terms of itself; he would do away with all transcendental factors in the explanation of reality. But modern psychological theory, Dewey believes, tends to shut thought in to the contemplation of its own subjective states, and thus gives it an extra-experiential status. A stimulus is said to strike upon an end organ, which sends an impulse to the cortex and there gives rise to a sensation which, as the effect of a stimulus, is representative of the real, but not real in itself. Thought, again, interprets the sensation, and sends out a motor impulse appropriate to the situation. These mental states and the thought which interprets them are, in Dewey's mind, wholly fictitious. The problem, then, is to give an account of the perceptual processes which shall eliminate the artificial states of mind and present mental operations as natural processes.