Phil.  Strictly speaking, Hylas, we do not see the same object that we feel; neither is the same object perceived by the microscope which was by the naked eye.  But, in case every variation was thought sufficient to constitute a new kind of individual, the endless number of confusion of names would render language impracticable.  Therefore, to avoid this, as well as other inconveniences which are obvious upon a little thought, men combine together several ideas, apprehended by divers senses, or by the same sense at different times, or in different circumstances, but observed, however, to have some connexion in nature, either with respect to co-existence or succession; all which they refer to one name, and consider as one thing.  Hence it follows that when I examine, by my other senses, a thing I have seen, it is not in order to understand better the same object which I had perceived by sight, the object of one sense not being perceived by the other senses.  And, when I look through a microscope, it is not that I may perceive more clearly what I perceived already with my bare eyes; the object perceived by the glass being quite different from the former.  But, in both cases, my aim is only to know what ideas are connected together; and the more a man knows of the connexion of ideas, the more he is said to know of the nature of things.  What, therefore, if our ideas are variable; what if our senses are not in all circumstances affected with the same appearances.  It will not thence follow they are not to be trusted; or that they are inconsistent either with themselves or anything else:  except it be with your preconceived notion of (I know not what) one single, unchanged, unperceivable, real Nature, marked by each name.  Which prejudice seems to have taken its rise from not rightly understanding the common language of men, speaking of several distinct ideas as united into one thing by the mind.  And, indeed, there is cause to suspect several erroneous conceits of the philosophers are owing to the same original:  while they began to build their schemes not so much on notions as on words, which were framed by the vulgar, merely for conveniency and dispatch in the common actions of life, without any regard to speculation.

HYL.  Methinks I apprehend your meaning.

Phil.  It is your opinion the ideas we perceive by our senses are not real things, but images or copies of them.  Our knowledge, therefore, is no farther real than as our ideas are the true representations of those originals.  But, as these supposed originals are in themselves unknown, it is impossible to know how far our ideas resemble them; or whether they resemble them at all.  We cannot, therefore, be sure we have any real knowledge.  Farther, as our ideas are perpetually varied, without any change in the supposed real things, it necessarily follows they cannot all be true copies of them:  or, if some are and others are not, it is impossible