§. 4.But besides the difficulties that lie more deep, and are of a more mysterious alloy; we are at a loss for a scientifical account even of our senses, the most knowable of our faculties. Our eyes, that see other things, see not themselves: and the foundations of knowledge are themselves unknown. That the soul is the sole percipient, which alone hath animadversion and sense properly so called, and that the body is only the receiver and conveyer of corporeal impressions, is as certain, as philosophy can make it. Aristotle himsels teaceth so much in that maxim of his Νους ορα, και νους ακουει [Greek: Nous ora, kai nous akouei]. And Plato credits this position with his suffrage; affirming, that 'tis the soul that hath life and sense, but the body neither. But this is so largely prosecuted by the great Descartes, and is a truth that shines so clear in the eyes of all considering men; that to go about industriously to prove it, were to light a candle to seek the sun: we'll therefore suppose it, as that which needs not arrest our motion; but yet, what are the instruments of sensible perceptions and particular conveyers of outward motions to the seat of sense, is difficult: and how the pure mind can receive information from that, which is not in the least like itself, and but little resembling what it represents; I think inexplicable. Whether sensation be made by corporal emissions and material ΕΙΔΩΛΑ [Greek: EIDOLA], or by notions impressed on the Ęthereal matter, and carried by the continuity thereof to the common sense; I'll not revive into a dispute: the ingenuity of the latter hath already given it almost an absolute victory over its rival. But suppose which we will, there are doubts not to be solved by either. For how the soul by mutation made in matter a substance of another kind, should be excited to action; and how bodily alterations and motions should concern that which is subject to neither; is a difficulty, which confidence may sooner triumph on, than conquer. For body cannot act on anything but by motion; motion cannot be received but by quantity and matter; the soul is a stranger to such gross substantiality, and owns nothing of these, but that it is clothed with by our deceived fancies; and therefore how can we conceive it subject to material impressions? And yet the importunity of pain, and unavoidableness of sensations strongly persuade, that we are so.
Besides, how is it, and by what art doth it read that such an image or stroke in matter (whether that of her vehicle, or of the brain, the case is the same) signifies such an object, did we learn an alphabet in our embryo-state? And how comes it to pass, that we are not aware of any such congenite apprehensions? We know what we know; but do we know any more? That by diversity of motions we should spell out figures, distances, magnitudes, colours, things not resembled by them; we must attribute to some secret deduction. But what this deduction should be, or by what mediums this knowledge is advanced; is as dark, as ignorance. One, that hath not the knowledge of letters, may see the figures; but comprehends not the meaning included in them: an infant may hear the sounds, and see the motion of the lips; but hath no conception conveyed by them, no knowing what they are intended to signify. So our souls, though they might have perceived the motions and images themselves by simile sense; yet without some implicit inference it seems inconceivable, how by that means they should apprehend their archetypes.
Moreover, images and motions are in the brain in a very inconsiderable latitude of space, and yet they represent the greatest magnitudes. The image of an hemisphere of the upper globe cannot be of a wider circumference, than a walnut: and how can such petty impressions notify such vastly expanded objects, but through some kind of scientifical method, and geometry in the principle? Without this it is not conceivable how distances should be perceived, but all objects would appear in a cluster, and lie in as narrow a room as their images take up in our scanter craniums. Nor will the philosophy of the most ingenious Descartes help us out: for, the striking of divers filaments of the brain, cannot well be supposed to represent distances, except some such kind of inference be allotted us in our faculties: the concession of which will only steed us as a refuge for ignorance: where we shall meet, what we would seem to shun.