206 Transactions.— Miscellaneous. 
The feelings or mental states of which we have experience comprise the 
comparatively vivid ones known as sensations and emotions, the fainter 
copies of these, sometimes called * ideas," which constitute the material of 
which thought is woven, and certain unique states of mind which form 
integral parts of volition and belief states of mind which assimilate most 
nearly to emotions, but which may be described as somewhat too colourless, 
if the term be allowable, to be fairly classed with these. 
All the real existences we know of being mental states, the totality of 
existence falls for each individual into two sections: his own mental states, 
i.e. mental states which form a part of his own consciousness, and mental 
states not his own. The former constitute a stream or chain, extending from 
a past that is more or less remote into a future almost wholly unknown ; 
his present condition of mind being a transverse section of the stream, or a 
link in the chain. His knowledge of the portion anterior to the present 
moment is obtained partly by the faculty of memory, and partly by a system 
of inferences; his anticipations as to the portion that is stil future are 
grounded entirely on inference. 
Now, by a process essentially identical with that by which he infers 
these future portions, and some of the past portions, of his own stream or 
chain of consciousness, each individual comes to believe, at a very early 
stage of his career, in the existence of other streams or chains of conscious- 
ness which are more or less like his own, but which are entirely outside 
it. He believes that his fellow-creatures are conscious beings, and that 
the higher animals are sentient. The process by which this conclusion is 
reached, and by which it may be justified, is fully described by Mr. Mill 
in a well-known passage of his “Examination of Sir William Hamilton’s 
Philosophy.” There is a further inference drawn which is of great impor- 
tance, and which I hope will engage our attention in a future paper. The 
inference is drawn that there exist relations of sequence and of synchronism 
between his own feelings and the feelings which compose the other streams 
of consciousness. These relations had already been recognized among his 
own feelings, and might easily be inferred as existing among the feelings of 
any other one stream of consciousness taken by itself. But it might seem 
a more perilous step to infer cross-relations of this kind between different 
streams; nevertheless, this inference, endorsed every hour a thousand times 
by the common sense of mankind, is one which I think can be shown to be 
logically justifiable. Without, however, dwelling any longer on this point, 
we may note that each individual conceives of other streams of conscious- 
ness as running parallel to his own in Time, and that their outsideness to 
his own consciousness is quite a different thing from the apparent outside- 
ness of any material body. A material body, or, as it is usually called in 
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