OF THE EXTERNAL SENSES. 311

The degrees of Heat and Cold which are agree-able, it has been found from experience , are like-wife healthful; and thofe which are difagreeable,umvholefome. The degree of their unwholefome-nefs, too, feems to be pretty much in proportionto that of their difagreeablenefs. If either of themis fo difagreeable as to be painful, it is generallydeftruftive; and that, too, in a very lliort periodof time. Thofe fenfations appear to have beengiven us for the prefervation of our own bodies.They necelfarily excite the defire of changing ourfituation when it is unwholefome or deflruflive;and when it is healthy, they allow us, or ratherthey entice us, to remain in it. But the defireof changing our fituation necelfarily fuppofes~fomeidea of externality; or of motion into a place dif-ferent from that in which we actually are; andeven the defire of remaining in the fame placefuppofes fome idea of at leaft the pollibility ofchanging. Thofe fenfations could not well haveanfwered the intention of Nature, had they notthus inftindlively fuggefled fome vague notion ofexternal exiftence.

That Sound, the objeft of the fenfe of Hearing,though perceived itfelf as in the ear, and nowherebut in the ear, may likewife, inflir.Hively, andantecedently to all obfervation and experience,obfcurely fuggeft fome vague notion of fome ex-ternal fubftance or tiling which excites it, I ammuch aifpofed to believe. I acknowledge, how-ever, that I have not been able to recollefl anyone inftance in which this fenfe feems fo diflin&ly