be found otherwise upon a fair examination; or if we have any wrong turn in our mind, how shall we ever apply a proper remedy, or even attempt to rectify it unless we know what it is? It is a false and mischievous shame that would prompt us to conceal ourselves from ourselves: nor does anything better show a true freedom and courage of thought than to search out the closest recesses of our heart impartially, and know all the persuasions, good or bad, that find harbor there.

CHAP. XIV.

KNOWLEDGE AND CONCEPTION.

ALTHOUGH Our knowledge all arises from our conception of things, and generally is more full and complete according as that is clearer, yet we know some things assuredly for true of which we cannot form any adequate conception. Different persons conceive variously of the same things, of which they all equally acknowledge the existence. Common people cannot easily conceive of opinions, tastes, sentiments, or inclinations, opposite to their own, though they see them exemplified in others: nor can they conceive the masterly performances of art or science, nor tricks of jugglers, nor anything out of the usual course of their experience: but such as have severally applied themselves to penetrate into those matters, find nothing surprising in them. For it is the repugnancy of objects to what we have ordinarily seen or known that renders them inconceivable, and therefore familiarity may make them easy to our apprehension. The savage cannot comprehend how men convey their thoughts to one another by writing, and the communication of them by sounds would appear as wonderful, but that mankind fall into that method before they know what wonder is, that is, before they have gained any experience, to which new appearances may seem repugnant.

The studious familiarize themselves to trains of observation peculiar to themselves; therefore, as they can clearly apprehend what remains a mystery to others, so on the other hand they find difficulties that nobody else can discern. The plain man makes no boggle at the ideas of creation, annihilation, or vacuity for he thinks he sees instances of them every day, in the production of plants from the ground, the consumption of fuel in the fire, and the emptiness of his pot every time he drinks out the liquor. But the naturalist considers that the materials composing the tree were

existing either in the earth, the air or the vapors, before it grew up, that the fire only divides the billet into imperceptible particles, and that after the liquor is all poured out of the pot it may yet remain full of light, or air, or ether: therefore he conceives no powers in nature that can either give or destroy existence, and disputes incessantly concerning the reality of a vacuum.

2. There are perhaps few more inexplicable ideas than that of force, whereby bodies act upon one another, and which may be divided into two sorts, impulse and resistance. The wheelwright, the millwright, and the gunner, can reason about it accurately and effectually to serve the purposes of their several arts; but the philosopher knows not what to make of it. It is neither substance, nor form, nor quality: as impulse, it is something imparted by external agents; as resistance, it is a property inherent in the body itself; yet resistance cannot subsist without an impulse received from some other body. It is the immediate cause of motion, nevertheless this cause may operate without producing its effect: for if you lay a dozen huge folios upon the table, they will press it strongly downwards with their weight, but the floor by its resistance presses it as strongly upwards; so the table, though receiving continual supplies of force remains immoveable.

Some things generally admitted for realities exceed the comprehensions of all men; as the velocity of light, travelling fifteen thousand miles in the swing of a clock pendulum, the greater velocity in the vibrations of ether, which we learn from Sir Isaac Newton overtake the rays of light, the minuteness of vessels carrying circulation, and performing secretion in the bodies of scarce visible insects, the eternity of time, immensity of space, and all infinities in general.

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As imagination takes her first impression from sensation, therefore I think we cannot form a clear conception of sensible objects whereof we have not had an idea conveyed by the senses. have not any direct notion of very swift or very slow motions, because properly speaking we do not see either, but only gather them from the change of position in the objects moving, which in the former case seem at once to fill the whole space taken up in their passage, and in the latter appear stationary; nor can we frame an idea of very small or very great magnitudes, otherwise than by enlarging the one in our fancy to a discernible size, and supposing the other removed to a distance that will lessen them within the compass of our vision. Neither perhaps can we conceive ideas of reflection whereof we have not experienced something similar passing in our own minds.

3. Things surpass our comprehension upon two accounts, either

when they are so unmanageable in themselves as that we cannot form any likeness of them in our imagination, which is the case of all infinitudes; or when we cannot conceive the manner in which they should be effected. I can easily conceive Dedalus flying in the air, for I have seen a print of him in Garth's Metamorphosis: but when I consider the weight of a man's body, the unwieldiness of wings sufficiently large to buoy him up, and the inability of his arms to flutter them fast enough, I cannot conceive the possibility of his ever practising that manner of travelling. Yet when we consider the small degree of force in rays of light, together with the solidity of glass, it seems as hard to conceive a possibility of their finding their way through so compact a body, as of Dedalus's flying: nevertheless constant experience convinces us of the fact.

When we have not an adequate conception of things themselves, nevertheless we may clearly affirm or deny something concerning them. Mr. Locke says we have a very confused idea of substance, and perhaps not a much better of form considered in the abstract; yet we may rest assured that form is not substance, nor substance form, and pronounce many other things concerning them without hesitation. And as imperfect notions as we have of force and impulse, or the manner of propagating motion, still we may easily apprehend a difference between the manner of imparting it from body to body, and from mind to body: for bodies only transmit the force they have received from elsewhere, nor can communicate more than they have themselves, and their re-action is always equal and opposite to action; but the mind produces an impulse she has not herself, nor does she ever feel the limbs re-act against her when she moves them: on the other hand, she receives a perception from the organs of sensation which had it not themselves, and returns not their impulse by a re-action, whenever they act upon her. Both those productions, of perception by body, and of motion by mind, appear alike incomprehensible, when we attempt to penetrate into the manner how they are ef fected.

4. But in order to understand ourselves the better, when we would go about to explain the manner in which causes produce their effects, let us consider what we generally mean by explanation. He that would explain the contrivance of a clock being made to strike the hours, begins with showing how the weights pull round the main wheel, how that by its teeth catches hold of the next wheel, and so he points out all the movements successively till he comes to the hammer and the bell. Or if he would explain the manner of nutrition, he tells you of the digestion of

the stomach, the secretion of chyle, its passage into the heart, the circulation of the blood, and thereby its dispersion throughout all parts of the flesh. Here we see that explaining is no more than enumerating the several parts of an operation, and tracing all the steps of its progress through intermediate causes and effects: therefore the manner of a remote effect being produced may be explained, but to call for an explanation of any cause operating immediately is absurd, because it is calling for an account of intermediate steps where there are none. In this case, we can only satisfy ourselves from experience, that such and such effects do constantly follow, upon the application of particular causes: all we can do further, is by remarking some difference in operations seemingly similar, as was attempted just now with respect to the action of mind and body, to prevent our mistaking one thing for another, not with an intent to give that as an explanation of either. To endeavor extending our idea beyond the cause operating, and the effect produced, would be to aim at apprehending more than the object really contains.

The quality we find in subjects of producing immediate effects, we call a primary property, but we cannot trace every phenomenon to this first source: there are many properties observable in bodies, which we are well satisfied result from the action of other bodies upon them, though we cannot investigate their operations. Such as the four kinds of attraction, namely, gravity, cohesion, magnetism, and electricity, the violence of fire, the sudden hardening of water by intense cold, the fusion of metals by intense heat, the vital circulation and secretion of humors in animals, and a multitude of the like sort, which a little reflection will easily suggest.

5. Number itself, whereon we can reason with the greatest accuracy and certainty of any subject, quickly exceeds our comprehension: it is a question with me whether we have a direct idea of any more than four, because beyond that little number we cannot tell how many objects lie before us upon inspection, without counting. Higher numbers we cannot ascertain, unless when by ranging them in order, which compounds the individuals into parcels, and thereby reduces them to fewer ideas, we can bring them within the compass of our apprehension: therefore we can presently reckon nine disposed into three equal rows, because then we need only consider them as three threes. The regular position of figures in numeration, and the contrivance of expressing the largest numbers by various combinations of a few numerals enables us to run those lengths we do in arithmetic. We talk currently of millions, and compute them with the utmost ex

actness, but our knowledge of two millions being double one million, is no more than the knowledge of two being the double of one and we know the value of figures only by the number of places they stand removed to the left. When we cast up the largest accounts, we have only three or four names or characters in our view at a time: and by this compendious artifice of drawing multitudes into so narrow a compass, we find means easily to manage objects that would be too cumbersome and extensive for us to conceive of themselves.

Nature abounds in mysteries, of which we may have a certain knowledge, but no clear conception: some are too large for imagination to grasp, some too minute for it to discern, others too obscure to be seen distinctly, and others, though plainly discernible in themselves, yet remain inexplicable in the manner of production, or appear incompatible with one another. Therefore, though conception be the groundwork of knowledge, and the inconceivableness of a thing a good argument against its reality, yet is it not an irrefragable one; for it may be overpowered by other proofs drawn from premises, whereof we have a clear conception and undoubted knowledge. I suppose it will be allowed that a man born blind can form no conception of light, nor how people can have sensations of objects at a vast distance, so as to determine thereby their magnitudes and situations: yet by conversing daily among mankind, he may find abundant reason to be satisfied of their possessing such a faculty. And as we proceed further in our investigation of nature, we shall find effects that cannot proceed from causes whereof we have had any experience, therefore must ascribe them to powers of which we can know nothing more than their being adequate to those effects; and what we know so imperfectly, we may justly pronounce inconceivable.

6. It is one of the most useful points of knowledge to distinguish, when the repugnancy of things to our common notions ought to make us reject them, and when not: for men have fallen into gross mistakes both ways. Some have been made to swallow the most palpable absurdities, under pretence that sense and reason are not to be trusted; others have denied facts verified by daily experience, because they could not conceive the manner wherein they were effected. There have been those who have disputed the reality of motion, of distance, of space, of bodies, of human action, upon account of some difficulties they could not reconcile to their ideas. I know of no other rule to go by in this point than that the strongest evidence ought always to prevail : wherefore nothing inconceivable in philosophy deserves credit, unless it