The knowledge we have comes from our senses, and the dogmatist can go no higher for the original of his certainty. Now let the sciolist tell me, why things must needs be so, as his individual senses represent them. Is he sure, that objects are not otherwise sensed by others, than they are by him? And why must his sense be the infallible criterion? it may be, what is white to us, is black to Negroes, and our angels to them are fiends. Diversity of constitution, or other circumstances varies the sensation, and to them of Java, pepper is cold. And though we agree in a common name, yet it may be, I have the same representation from yellow, that another hath from green. Thus two look upon an alabaster statue; he calls it white, and I assent to the appellation: but how can I discover, that his inward sense on't is the same that mine is? It may be alabaster is represented to him, as jet is to me, and yet it is white to us both. We accord in the name: but it's beyond our knowledge, whether we do so in the conception answering it. Yea, the contrary is not without its probability. For though the images, motions, or whatever else is the cause of sense, may be alike as from the object; yet may the representations be varied according to the nature and quality of the recipient. That's one thing to us looking through a tube, which is another to our naked eyes. The same things seem otherwise through a green glass, than they do through a red. Thus objects have a different appearance, when the eye is violently any way distorted, from that they have, when our organs are in their proper site and figure, and some extraordinary alterations in the brain duplicate that which is but a single object to our undistempered sentient. Thus, that's of one colour to us standing in one place, which hath a contrary aspect in another: as in those versatile representations in the neck of a dove, and folds of scarlet. And as great diversity might have been exemplified in the other senses, but for brevity I omit them. Now then, since so many various circumstances concur to every individual constitution, and every man's senses, differing as much from others in its figure, colour, site, and infinite other particularities in the organization, as any one man's can from itself, through divers accidental variations: it cannot well be supposed otherwise, but that the conceptions conveyed by them must be as diverse. Thus, one man's eyes are more protuberant, and swelling out; another's more sunk and depressed. One man's bright, and sparkling, and as it were swimming in a subtle, lucid moisture; another's more dull and heavy, and destitute of that spirituous humidity. The colour of men's eyes is various, nor is there less diversity in their bigness. And if we look further into the more inward constitution, there's more variety in the internal configurations, than in the visible outside. For let us consider the different qualities of the optic nerves, humours, tumours and spirits; the diverse figurings of the brain; the strings, or filaments thereof; their difference in tenuity and aptness for motion: and as many other circumstances, as there are individuals in human nature; all these are diversified according to the difference of each crasis, and are as unlike, as our faces. From these diversities in all likelihood will arise as much difference in the manner of the reception of the images, and consequently as various sensations. So then, how objects are represented to myself, I cannot be ignorant, being conscious to mine own cogitations; but in what manner they are received, and what impresses they make upon the so differing organs of another, he only knows, that feels them.
There is an obvious, an easy objection, which I have sufficiently caveated against; and with the considerate it will signify no more than the inadvertency of the objectors. 'Twill be thought by sight discerners a ridiculous paradox, that all men should not conceive of the objects of sense alike; since their agreement in the appellation seems so strong an argument of the identity of the sentiment. All, for instance, say, that snow is white, and that jet is black, is doubted by none. But yet 'tis more than any man can determine, whether his conceit of what he calls white, be the same with another's; or whether, the notion he hath of one colour be not the same another hath of a very diverse one. So then, to direct all against the knowing ignorant, what he hath of sensible evidence, the very ground work of his demonstration, is but the knowledge of his own resentment: but how the same things appear to others, they only know, that are conscious to them; and how they are in themselves only he that made them.
Thus have I in this last particular played with the dogmatist in a personated skepticism: and would not have the design of the whole discourse measured by the seeming tendency of this part on't. The sciolist may here see, that what he counts of all things most absurd and irrational, hath yet considerable show of probability to plead its cause, and it may be more than some of his presumed demonstrations. 'Tis irreprehensible in physicians to cure their patient of one disease by casting him into another, less desperate. And I hope, I shall not deserve the frown of the ingenuous for my innocent intentions; having in this only imitated the practice of bending a crooked stick as much the other way, to straighten it. And if by this verge to the other extreme, I can bring the opinionative confident but half the way, viz, that discreet modest equipoise of judgment, that becomes the sons of Adam; I have compassed what I aim at.