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The opinions of the ancient philosophers, their fictions of substance and accident, and their reasonings concerning substantial forms and occult qualities, are like the spectres in the dark, and are derived from principles, which, however common, are neither universal nor unavoidable in human nature. The modern philosophy pretends to be entirely free from this defect, and to arise only from the solid, permanent, and consistent principles of the imagination. Upon what grounds this pretension is founded, must now be the subject of our inquiry.
The fundamental principle of that philosophy is the opinion concerning colours, sounds, tastes, smells, heat and cold; which it asserts to be nothing but impressions[Pg 291] in the mind, derived from the operation of external objects, and without any resemblance to the qualities of the objects. Upon examination, I find only one of the reasons commonly produced for this opinion to be satisfactory; viz. that derived from the variations of those impressions, even while the external object, to all appearance, continues the same. These variations depend upon several circumstances. Upon the different situations of our health: a man in a malady feels a disagreeable taste in meats, which before pleased him the most. Upon the different complexions and constitutions of men: that seems bitter to one, which is sweet to another. Upon the difference of their external situation and position: colours reflected from the clouds change according to the distance of the clouds, and according to the angle they make with the eye and luminous body. Fire also communicates the sensation of pleasure at one distance, and that of pain at another. Instances of this kind are very numerous and frequent.
The conclusion drawn from them, is likewise as satisfactory as can possibly be imagined. 'Tis certain, that when different impressions of the same sense arise from any object, every one of these impressions has not a resembling quality existent in the object. For as the same object cannot, at the same time, be endowed with different qualities of the same sense, and as the same quality cannot resemble impressions entirely different; it evidently follows, that many of our impressions have no external model or archetype. Now, from like effects we presume like causes. Many of the impressions of colour, sound, &c., are confessed to be nothing but internal existences, and to arise from causes, which no ways resemble them. These impressions[Pg 292] are in appearance nothing different from the other impressions of colour, sound, &c. We conclude, therefore, that they are, all of them, derived from a like origin.
This principle being once admitted, all the other doctrines of that philosophy seem to follow by an easy consequence. For, upon the removal of sounds, colours, heat, cold, and other sensible qualities, from the rank of continued independent existences, we are reduced merely to what are called primary qualities, as the only real ones, of which we have any adequate notion. These primary qualities are extension and solidity, with their different mixtures and modifications; figure, motion, gravity and cohesion. The generation, increase, decay and corruption of animals and vegetables, are nothing but changes of figure and motion; as also the operations of all bodies on each other; of fire, of light, water, air, earth, and of all the elements and powers of nature. One figure and motion produces another figure and motion; nor does there remain in the material universe any other principle, either active or passive, of which we can form the most distant idea.
I believe many objections might be made to this system; but at present I shall confine myself to one, which is, in my opinion, very decisive. I assert, that instead of explaining the operations of external objects by its means, we utterly annihilate all these objects, and reduce ourselves to the opinions of the most extravagant scepticism concerning them. If colours, sounds, tastes and smells be merely perceptions, nothing, we can conceive, is possessed of a real, continued, and independent existence; not even motion, extension and solidity, which are the primary qualities chiefly insisted on.
To begin with the examination of motion; 'tis evident this is a quality altogether inconceivable alone, and without a reference to some other object. The idea of motion necessarily supposes that of a body moving. Now, what is our idea of the moving body, without which motion is incomprehensible? It must resolve itself into the idea of extension or of solidity; and consequently the reality of motion depends upon that of these other qualities.
This opinion, which is universally acknowledged concerning motion, I have proved to be true with regard to extension; and have shown that 'tis impossible to conceive extension but as composed of parts, endowed with colour or solidity. The idea of extension is a compound idea; but as it is not compounded of an infinite number of parts or inferior ideas, it must at last resolve itself into such as are perfectly simple and indivisible. These simple and indivisible parts not being ideas of extension, must be nonentities, unless conceived as coloured or solid. Colour is excluded from any real existence. The reality therefore of our idea of extension depends upon the reality of that of solidity; nor can the former be just while the latter is chimerical. Let us then lend our attention to the examination of the idea of solidity.
The idea of solidity is that of two objects, which, being impelled by the utmost force, cannot penetrate each other, but still maintain a separate and distinct existence. Solidity therefore is perfectly incomprehensible alone, and without the conception of some bodies which are solid, and maintain this separate and distinct existence. Now, what idea have we of these bodies? The ideas of colours, sounds, and other secondary qualities, are excluded. The idea of motion[Pg 294] depends on that of extension, and the idea of extension on that of solidity. 'Tis impossible, therefore, that the idea of solidity can depend on either of them. For that would be to run in a circle, and make one idea depend on another, while, at the same time, the latter depends on the former. Our modern philosophy, therefore, leaves us no just nor satisfactory idea of solidity, nor consequently of matter.
This argument will appear entirely conclusive to every one that comprehends it; but because it may seem abstruse and intricate to the generality of readers, I hope to be excused if I endeavour to render it more obvious by some variation of the expression. In order to form an idea of solidity, we must conceive two bodies pressing on each other without any penetration; and 'tis impossible to arrive at this idea, when we confine ourselves to one object, much more without conceiving any. Two nonentities cannot exclude each other from their places, because they never possess any place, nor can be endowed with any quality. Now I ask, what idea do we form of these bodies or objects to which we suppose solidity to belong? To say that we conceive them merely as solid, is, to run on in infinitum. To affirm that we paint them out to ourselves as extended, either resolves all into a false idea, or returns in a circle. Extension must necessarily be considered either as coloured, which is a false idea, or as solid, which brings us back to the first question. We may make the same observation concerning mobility and figure; and, upon the whole, must conclude, that after the exclusion of colours, sounds, heat and cold, from the rank of external existences, there remains nothing which can afford us a just and consistent idea of body.
