234 THOUGHTS ON BELIEF AND EVIDENCE. 



feeling on the subject as others, which is not an inference true or 

 false, but something so involved in the mode of our receiving the 

 sensations, that to have the sensations is to believe not in them only, 

 but in their external causes, nor is it easy to conceive of such an 

 invariable effect, iu all minds, being delusive and unreliable. But 

 whatever may be said of the external causes, the existence of the 

 sensations is undeniable, and to experience them is to believe them, 

 there being no place for any evidence on the subject. It may be 

 Baid that we are deceived even in our sensations, having afterwards, if 

 not at the moment, full assurance that certain supposed perceptions 

 of our organs of seuse were not to be trusted ; or, if we remain under 

 the delusion, it being fully known to others that we are misled, so 

 that a reasonable man would not rely too firmly even on the evidence 

 of sense. There is some truth in this, yet not so as to invalidate our 

 previous statement respecting our belief in our sensations. The 

 mental states so termed, arise out of states of certain nerves, which 

 states convey to us the notion of real things, existing independently 

 of us, and becoming, by their means, known to us. But there is 

 another class of mental states, distinguished by many philosophers 

 as ideas — that term being used as contrasted with sensations — the 

 connection of which with affections of the nervous system may also 

 be well proved, and which appear really to differ from sensations 

 chiefly in the degree of vividness of the nervous action. Now it is 

 an ascertained fact that, under the influence of disease, producing 

 abnormal excitement of the nervous system, or some part of it, these 

 ideas may have, to the individual experiencing them, all the force 

 of sensations, so that he receives them as such, or, in other words, 

 believes in the reality of what is thus brought before his mind. It is 

 from other persons in full health being in a position to receive the 

 same sensations, and not receiving them, or from their comparison 

 with facts well known to great numbers, that we are assured that what 

 the individual supposes himself to perceive has no reality, and that 

 he is under the influence of disease, which may amount to madness, 

 or may be only partial, connected with disorder of a particular organ, 

 and of such kind that the patient, though believing in the false 

 sensations for the moment, can convince himself of their real nature, 

 and correct, by his judgment, the delusion to which he has been 

 subject. There is also another class of deceptions, usually regarded 

 as deceptions of the senses, but really consisting in so strong au 



