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exactly, or more immediately, with the fenfations received by the other fenfes. Yet the fhort-fighted, as well as they who have the acuteft fight, truft to this fenfe, as foon as they are placed in a fituation favourable to accurate obfervation: all the difference is, that it is more difficult, and often more inconvenient, for fhort-fighted perfons to place themselves in fuch a fituation. Still it fhould be remembered, that a perfect fenfe and a well-informed fenfe are not fynonymous terms. We call a fenfe well-informed, in oppofition to one that is depraved or fallacious. Perfection and imperfection of fenfe are relative terms; implying a comparison, either between different men, in respect of the acutenefs of their fenfes and faculties; or between any fenfe, as it appears in a particular man, and the degree of acuteness which is found to belong to that fenfe as it appears in the generality of mankind. There are two telefcopes, one of which gives a diftinct view of an object at two, and the other at four miles distance both are equally well-informed, (if may fo fpeak); that is, equally true in their representations; but the one is much more imperfect than the other.
I do not, at prefent, offer any further illuftrations of these criteria of a well-informed fenfe. The reader who examines them by the rules of common prudence, will perhaps be fatisfied with them: at least I am apt to think, that few will fufpect the veracity of
their faculties when they stand this test. But let it not be fuppofed, that I mean to infinuate, that a man never trufts his faculties till he first examine them after this manner : we believe our fenfes previously to all reflection or examination; and we never disbelieve them, but upon the authority of our fenfes placed in circumstances more favourable to accurate obfervation.
If the reader is not fatisfied with these criteria, it is no great matter. The question concerning a well-informed fenfe it is not perhaps easy to answer. I offer these remarks rather as hints to be attended to by other adventurers in this part of science, than as a complete folution of the difficulty. If it were not that I presume fome advantage may be derived from them in this way, I should have omitted them altogether; for on them does not depend the doctrine I mean to establifh.
The fubject continued. guishable into claffes.
Intuitive truths diftin'
F the notions attending the perception of certain truth, we formerly mentioned this as one, "That in regard to fuch truth,
we fuppofe we fhould entertain the fame "fentiments and belief if we were perfectly "acquainted with all nature *. Left it fhould be thought that we mean to extend this notion too far, it feems proper to introduce here the following remarks.
1. The axioms and demonftrated conclufions of geometry are certainly true, and certainly agreeable to the nature of things. Thus we judge of them at prefent; and thus we neceffarily believe, that we fhould judge of them, even if we were endued with omnifcience and infallibility. It is a natural dictate of human understanding, that the contrary of these truths muft for ever remain abfurd and impoffible; and that omnipotence itfelf cannot change their nature; tho' it might fo deprave our judgement, as to make us difbelieve, or not perceive them t. 2. That
*Sce part 1. chap. 1.
Some authors are of opinion, that all mathematical truth is refolveable into identical propofitions. The following remark to this purpofe is taken from a Differtation on Evidence, printed at Berlin in the year 1764. "Omnes mathematicorum propofitioncs funt identic, "et repræfentantur hac formula, a=a. Sunt veritates
"identicæ, fub varia forma expreffæ, imo ipfum, quod "dicitur, contradictionis principium, vario modo enunciatum et involutum ; fiquidem omnes hujus generis propofitiones revera in eo contineantur. Secundum "noftram autem intelligendi facultatem ca eft propofi"tionum differentia, quod quædam longa ratiociniorum "ferie, alia autem breviori via, ad primum omnium "principium reducantur, et in illud refolvantur. Sic.
2. That my body exifts, and is endued with a thinking, active, and permanent principle, which I call my foul;-That the material world hath fuch an existence as the vulgar afcribe to it, that is, a real separate existence, to which its being perceived is in no wife neceffary; ;-That the men, beafts, houfes, and mountains, we fee and feel around us, are not imaginary, but real and material beings, and fuch, in respect of shape and tangible magnitude, as they appear to our fenfes; I am not only confcious that I believe, but also certain, that fuch is the nature of these things; and that, thus far at least, in regard to the nature of these things, an omniscient and infallible being cannot think me mistaken. Of thefe truths I am fo certain, that I fcruple not to pronounce every being in an error who is of a contrary fentiment concerning them. For fuppofe an in
"vg. propofitio 2+2=4, ftatim huc cedit 1+1+1+1=
I+I+I+I, i. e. idem eft idem; et, proprie loquen"do, hoc modo enunciari debet. Si contingat, adeffe "vel exiftere quatuor entia, tum exiftunt quatuor entia'; nam de exiftentia non agunt geometræ, fed ea hypo"thetice tantum fubintelligitur. Inde fumma oritur cer
titudo ratiocinia perfpicienti; obfervat nempe idearum "identitatem; et hæc eft evidentia, affenfum immediate "cogens, quam mathematicam aut geometricam voca<< mus. Mathefi tamen fua natura priva non eft et pro"pria; oritur etenim ex identitatis perceptione, quæ "locum habere poteft, etiamfi ideæ non repræfentent "extenfum." Of the connection of geometrical axioms with identical propofitions, fee Dr Campbell's Philofophy of Rhetorick, book 1. chap. 5. fect. 1.
telligent creature, an angel for inftance, to believe that there are not in the universe any fuch things as this folar fyftem, this earth, these mountains, houfes, animals, this being whom I call myfelf; could I, by any effort, bring myself to believe, that his opinion is a true one, and implies a propofition expreffive of fomething agreeable to the nature of things? It is impoffible and inconceivable. My understanding intimates, that such an opinion would as certainly be false, as it is falfe that two and two are equal to ten, or that things equal to one and the fame thing are unequal to one another. Yet this is an opinion which omnipotence could render true, by annihilating the whole of this folar fyftem; or make me admit as true, by depriving me of understanding. But fo long as this folar system remains unannihilated, and my intellect undepraved, there is not a geometrical axiom more true, or more evident to me, than that this folar fyftem, and all the objects above mentioned, do exift; there is not a geometrical axiom that has any better title to be accounted a principle of human knowledge; there is not a geometrical axiom against which it is more abfurd, more unreafonable, more unphilofophical, to argue. 3. That fnow is white, fire hot, gold yellow, and fugar fweet, we believe to be certainly true. Thefe bodies affect our eyes, touch, and palate, in a peculiar manner; and we have no reason to think, that they affect