Now, if that faint reproduction of a sensation, which we call the memory of it, is properly termed a thought, it seems to me to be a somewhat forced proceeding to draw a hard and fast line of demarcation between thoughts and sensations. If sensations are not rudimentary thoughts, it may be said that some thoughts are rudimentary sensations. No amount of sound constitutes an echo, but for all that no one would pretend that an echo is something of totally different nature from a sound. Again, nothing can be looser, or more inaccurate, than the assertion that "sensations supply the conditions for the existence of thought or knowledge." If this implies that sensations supply the conditions for the existence of our memory of sensations or of our thoughts about sensations, it is a truism which it is hardly worth while to state so solemnly. If it implies that sensations supply anything else, it is obviously erroneous. And if it means, as the context would seem to show it does, that sensations are the subject-matter of all thought or knowledge, then it is no less contrary to fact, inasmuch as our emotions, which constitute a large part of the subject-matter of thought or of knowledge, are not sensations. More eccentric still is the Quarterly Reviewer's next piece of psychology. "Altogether, we may clearly distinguish at least six kinds of action to which the nervous system ministers:-- "I. That in which impressions received result in appropriate movements without the intervention of sensation or thought, as in the cases of injury above given.--This is the reflex action of the nervous system. "II. That in which stimuli from without result in sensations through the agency of which their due effects are wrought out.--Sensation. "III. That in which impressions received result in sensations which give rise to the observation of sensible objects.--Sensible perception. "IV. That in which sensations and perceptions continue to coalesce, agglutinate, and combine in more or less complex aggregations, according to the laws of the association of sensible perceptions.--Association. "The above four groups contain only indeliberate operations, consisting, as they do at the best, but of mere _presentative_ sensible ideas in no way implying any reflective or _representative_ faculty. Such actions minister to and form _Instinct_. Besides these, we may distinguish two other kinds of mental action, namely:-- "V. That in which sensations and sensible perceptions are reflected on by thought, and recognised as our own, and we ourselves recognised by ourselves as affected and perceiving.--Self-consciousness. "VI. That in which we reflect upon our sensations or perceptions, and ask what they are, and why they are.--Reason.