But, however this may be, our sensations and perceptions of material phenomena are attendant on the excitation of certain motions in the anterior parts of the brain. Whenever certain motions are excited in this substance, certain sensations and ideas of resistance, extension, &c., are either concomitant, or ensue within a period too brief for our cognisance. It is these sensations and ideas that we directly cognise, and it is to them that we have attached the idea of the particular kind of matter we happen to be thinking of. As this idea is not like the thing itself, so neither is it like the motions in our brain on which it is attendant. It is no more like these than, say, a stone is like the individual characters, written or spoken, that form the word “stone,” or than these last are, in sound, like the word “stone” itself, whereby the idea of a stone is so immediately and vividly presented to us. True, this does not involve that our idea shall not resemble the object that gave rise to it, any more than the fact that a looking-glass bears no resemblance to the things reflected in it involves that the reflection shall not resemble the things reflected; the shifting nature, however, of our ideas and conceptions is enough to show that they must be symbolical, and conditioned by changes going on within ourselves as much as by those outside us; and if, going behind the ideas which suffice for daily use, we extend our inquiries in the direction of the reality underlying our conception, we find reason to think that the brain-motions which attend our conception correspond with exciting motions in the object that occasions it, and that these, rather than anything resembling our conception itself, should be regarded as the reality. This leads to a third matter, on which I can only touch with extreme brevity.