The persons then, who refine with Berkeley upon the system of things so far, as to deny that there is any such thing as matter in the sense in which it is understood by the writers on natural philosophy, proceed on the ground of affirming that we have no reason to believe that the causes of our sensations have an express resemblance to the sensations themselves[81]. That which gives us a sensation of colour is not itself coloured: and the same may be affirmed of the sensations of hot and cold, of sweet and bitter, and of odours offensive or otherwise. The immaterialist proceeds to say, that what we call matter has been strewn to be so exceedingly porous, that, for any thing we know, all the solid particles in the universe might be contained in a nutshell, that there is no such thing in the external world as actual contact, and that no two particles of matter were ever so near to each other, but that they might be brought nearer, if a sufficient force could be applied for that purpose. From these premises it seems to follow with sufficient evidence, that the causes of our sensations, so far as the material universe is concerned, bear no express resemblance to the sensations themselves.
[81] See above, Essay XXI.
How then does the question stand with relation to mind? Are those persons who deny the existence of matter, reduced, if they would be consistent in their reasonings, to deny, each man for himself, that he has any proper evidence of the existence of other minds than his own?
He denies, while he has the sensation of colour, that there exists colour out of himself, unless in thinking and percipient beings constituted in a manner similar to that in which he is constituted. And the same of the sensations of hot and cold, sweet and bitter, and odours offensive or otherwise. He affirms, while he has the sensation of length, breadth and thickness, that there is no continuous substance out of himself, possessing the attributes of length, breadth and thickness in any way similar to the sensation of which he is conscious. He professes therefore that he has no evidence, arising from his observation of what we call matter, of the actual existence of a material world. He looks into himself, and all he finds is sensation; but sensation cannot be a property of inert matter. There is therefore no assignable analogy between the causes of his sensations, whatever they may be, and the sensations themselves; and the material world, such as we apprehend it, is the mere creature of his own mind.
Let us next consider how this question stands as to the conceptions he entertains respecting the minds of other men.
That which gives him the sensation of colour, is not any thing coloured out of himself; and that which gives him the sensation of length, breadth and thickness, is not any thing long, broad and thick in a manner corresponding with the impression he receives. There is nothing in the nature of a parallel, a type and its archetype, between that which is without him and that which is within, the impresser and the impression. This is the point supposed to be established by Locke and Newton, and by those who have followed the reasonings of these philosophers into their remotest consequences.
But the case is far otherwise in the impressions we receive respecting the minds of other men. In colour it has been proved by these authors that there is no express correspondence and analogy between the cause of the sensation and the sensation.
They are not part and counterpart. But in mind there is a precise resemblance and analogy between the conceptions we are led to entertain respecting other men, and what we know of ourselves. I and my associate, or fellow-man, are like two instruments of music constructed upon the same model. We have each of us, so to speak, the three great divisions of sound, base, tenor and treble. We have each the same number of keys, capable of being struck, consecutively or with alternations, at the will of the master. We can utter the same sound or series of sounds, or sounds of a different character, but which respond to each other. My neighbour therefore being of the same nature as myself, what passes within me may be regarded as amounting to a commanding evidence that he is a real being, having a proper and independent existence.
There is further something still more impressive and irresistible in the notices I receive respecting the minds of other men. The sceptics whose reasonings I am here taking into consideration, admit, each man for himself, the reality of his own existence.
There is such a thing therefore as human nature; for he is a specimen of it. Now the idea of human nature, or of man, is a very complex thing. He is in the first place the subject of sensible impressions, however these impressions are communicated to him. He has the faculties of thinking and feeling. He is subject to the law of the association of ideas, or, in other words, any one idea existing in his mind has a tendency to call up the ideas of other things which have been connected with it in his first experience. He has, be it delusive or otherwise, the sense of liberty of action.
But we will go still further into detail as to the nature of man.
Our lives are carried forward by the intervention of what we call meat, drink and sleep. We are liable to the accidents of health and sickness. We are alternately the recipients of joy and sorrow, of cheerfulness and melancholy. Our passions are excited by similar means, whether of love or hatred, complacency or indignation, sympathy or resentment. I could fill many pages with a description of the properties or accidents, which belong to man as such, or to which he is liable.
Now with all these each man is acquainted in the sphere of his inward experience, whether he is a single being standing by himself, or is an individual belonging to a numerous species.
