fhewn to be reflected within the substance of a homogeneous tranfparent body, there can be no reason from fact, and appearances, to conclude that they have any fuch folid parts; but, on the contrary, there must be all the reafon in the world to believe, that no fuch folid refifting particles exift. All the phenomena may be explained without them, and indeed cannot be explained with them. Since then it is demonftrable that no common preffure is fufficient to bring bodies even into feeming contact, or that near approach which the component parts of the fame body make to each other (though these are by no means in abfolute contact, as the phenomena of heat and cold fully prove) but the resistance to a nearer approach is in all cafes caused by powers of repulfion, there can be no fufficient reafon to afcribe refiftance in any cafe to any thing befides fimilar powers. Nay, the eftablished rules of philofophizing above recited, abfolutely require that we afcribe all refiftance to fuch powers; and confequently the fuppofition of the folidity or impenetrability of matter, derived folely from the confideration of the refiftance of the folid parts of bodies (which, exclufive of a power operating at a diftance from them, cannot be proved to have any refiftance) appears to be deftitute of all fupport whatever. The hypothefis was fuggested by a mere fallacy, and therefore ought to be difcarded now that the fallacy is discovered. It It will be faid, that if matter be not a folid or impenetrable fubftance, what is it? I anfwer, with refpect to this, as I fhould with respect to any other fubftance, that it is poffeffed of fuch properties, and fuch only, as the actual well-examined appearances prove it to be poffeffed of. That it is poffeffed of powers of attraction and repulfion, and of feveral fpheres of them, one within another, I know; becaufe appearances cannot be explained without fuppofing them; but that there is any thing in, or belonging to matter, capable of refiftance, befides those powers of repulfion, does not appear from any phenomena that we are yet acquainted with; and, therefore, as a philofopher, I am not authorized to conclude that any fuch a thing exifts. On the contrary, I am obliged to deny that matter has fuch a property. If I be afked how, upon this hypothefis matter differs from Spirit, if there be nothing in matter that is properly folid or impenetrable; I answer, that it no way concerns me, or true philofophy, to maintain that there is any fuch difference between them as has hitherto been fuppofed. On the contrary, I confider the notion of the union and mutual influences of fubftances fo effentially different from one another, as material and immaterial fubftances have been reprefented, as an opinion attended with difficulties infinitely embarraffing, and indeed actually infuperable, as as may appear in the fequel of these difquifi tions. The confiderations fuggefted above tend to remove the odium which has hitherto lain upon matter, from its fuppofed neceffary property of folidity, inertness, or sluggishness; as from this circumftance only the bafeness and imperfection, which have been afcribed to it are derived. Since matter has, in fact, no properties but thofe of attraction and repulsion, it ought to rife in our efteem, as making a nearer approach to the nature of spiritual and immaterial beings, as we have been taught to call thofe which are opposed to grofs matter. The principles of the Newtonian philofophy were no fooner known, than it was feen how few, in comparifon, of the phenomena of nature, were owing to folid matter, and how much to powers, which were only fuppofed to accompany and furround the folid parts of matter. It has been afferted, and the affertion has never been difproved, that for any thing we know to the contrary, all the folid matter in the folar system might be contained within a nut-fhell, there is fo great a proportion of void space within the fubftance of the most solid bodies. Now when folidity had apparently fo very little to do in the fyftem, it is really a wonder that it did not occur to philofophers fooner, that perhaps there might be nothing for it to do at all, and that there might be no fuch a thing in nature. C Since Since the only reafon why the principle of thought, or fenfation, has been imagined to be incompatible with matter, goes upon the fuppofition of impenetrability being the effential property of it, and confequently that folid extent is the foundation of all the properties that it can poffibly fuftain, the whole argument for an immaterial thinking principle in man, on this new fuppofition, falls to the ground; matter, deftitute of what has hitherto been called folidity, being no more incompatible with fenfation and thought, than that fubftance, which, without knowing any thing farther about it, we have been used to call immaterial. I will add in this place, though it will be confidered more fully hereafter, that this fuppofition, of matter having no other properties befides thofe of attraction and repulfion, greatly relieves the difficulty which attends the fuppofition of the creation of it out of nothing, and alfo the continual moving of it by a being who has hitherto been fuppofed to have no common property with it. For, according to this hypothesis, both the creating mind, and the created fubftance are equally deftitute of folidity or impenetrability; so that there can be no difficulty whatever in fupposing that the latter may have been the offfpring of the former. This opinion, which I here maintain, of the penetrability of matter, is not my own, but what, 19 what, from a conviction of its truth, I have adopted from Father Bofcovich, and Mr. Michell, to both of whom, independently of each other, this theory had occurred. Their ideas upon this fubject, I have represented in my Hiftory of Difcoveries relating to Vifion, Light, and Colours; and as the doctrine is there placed in fomewhat of a different light, and in language chiefly borrowed from my authors, I fhall, in order to throw greater light on the fubject, quote the whole paffage relating to it in this place, and with it fhall close this section. "The easiest method of folving all the dif"ficulties attending the fubject of the fubtlety of light, and of answering Mr. Euler's objections to its materiality, is to adopt the hypothefis of Mr. Bofcovich, who fup"poses that matter is not impenetrable, as "before him it had been univerfally taken "for granted; but that it confifts of phyfical points only, endued with powers of attrac"tion and repulfion, taking place at different "diftances, that is, furrounded with various spheres of attraction and repulfion; in the "fame manner as folid matter is generally "fuppofed to be. Provided, therefore, that any body move with a fufficient degree of velocity, or have fufficient momentum to "overcome any powers of repulfion that it may meet with, it will find no difficulty "in making its way through any body what"ever, for nothing will interfere, or pene C 2 ❝trate |