its first and most natural tendency. But when we compare experiments, and reason a little upon them, we quickly perceive, that the doctrine of the independent existence of our sensible perceptions is contrary to the plainest experience. This leads us backward upon our footsteps to perceive our error in attributing a continued existence to our perceptions, and is the origin of many very curious opinions, which we shall here endeavour to account for.
'Twill first be proper to observe a few of those experiments, which convince us, that our perceptions are not possessed of any independent existence. When we press one eye with a finger, we immediately perceive all the objects to become double, and one half of them to be removed from their common and natural position. But as we do not attribute a continued existence to both these perceptions, and as they are both of the same nature, we clearly perceive, that all our perceptions are dependent on our organs, and the disposition of our nerves and animal spirits. This opinion is confirmed by the seeming increase and diminution of objects according to their distance; by the apparent alterations in their figure; by the changes in their colour and other qualities, from our sickness and distempers, and by an infinite number of other experiments of the same kind; from all which we learn, that our sensible perceptions are not possessed of any distinct or independent existence.
The natural consequence of this reasoning should be, that our perceptions have no more a continued than an independent existence; and, indeed, philosophers have so far run into this opinion, that they change their system, and distinguish (as we shall do for the future) betwixt perceptions and objects, of which the former are supposed to be interrupted and perishing, and different at every different return; the latter to be uninterrupted, and to preserve a continued existence and identity. But however philosophical this new system may be esteemed, I assert that 'tis only a palliative remedy, and that it contains all the difficulties of the vulgar system, with some others that are peculiar to itself. There are no principles either of the understanding or fancy, which lead us directly to embrace this opinion of the double existence of perceptions and objects, nor can we arrive at it but by passing through the common hypothesis of the identity and continuance of our interrupted perceptions. Were we not first persuaded that our perceptions are our only objects, and continue to exist even when they no longer make their appearance to the senses, we should never be led to think that our perceptions and objects are different, and that our objects alone preserve a continued existence. "The latter hypothesis has no primary recommendation either to reason or the imagination, but acquires all its influence on the imagination from the former." This proposition contains two parts, which we shall endeavour to prove as distinctly and clearly as such abstruse subjects will permit.
As to the first part of the proposition, _that this philosophical hypothesis has no primary recommendation, either to reason or the imagination_, we may soon satisfy ourselves with regard to _reason_, by the following reflections. The only existences, of which we are certain, are perceptions, which, being immediately present to us by consciousness, command our strongest assent, and are the first foundation of all our conclusions. The only conclusion we can draw from the existence of one thing to that of another, is by means of the relation of cause and effect, which shows, that there is a connexion betwixt them, and that the existence of one is dependent on that of the other. The idea of this relation is derived from past experience, by which we find, that two beings are constantly conjoined together, and are always present at once to the mind. But as no beings are ever present to the mind but perceptions, it follows, that we may observe a conjunction or a relation of cause and effect between different perceptions, but can never observe it between perceptions and objects.
'Tis impossible, therefore, that from the existence or any of the qualities of the former, we can ever form any conclusion concerning the existence of the latter, or ever satisfy our reason in this particular.
'Tis no less certain, that this philosophical system has no primary recommendation to the _imagination_, and that that faculty would never, of itself, and by its original tendency, have fallen upon such a principle. I confess it will be somewhat difficult to prove this to the full satisfaction of the reader; because it implies a negative, which in many cases will not admit of any positive proof. If any one would take the pains to examine this question, and would invent a system, to account for the direct origin of this opinion from the imagination, we should be able, by the examination of that system, to pronounce a certain judgment in the present subject. Let it be taken for granted, that our perceptions are broken and interrupted, and, however like, are still different from each other; and let any one, upon this supposition, show why the fancy, directly and immediately, proceeds to the belief of another existence, resembling these perceptions in their nature, but yet continued, and uninterrupted, and identical; and after he has done this to my satisfaction, I promise to renounce my present opinion. Meanwhile I cannot forbear concluding, from the very abstractedness and difficulty of the first supposition, that 'tis an improper subject for the fancy to work upon. Whoever would explain the origin of the _common_ opinion concerning the continued and distinct existence of body, must take the mind in its _common_ situation, and must proceed upon the supposition, that our perceptions are our only objects, and continue to exist even when they are not perceived. Though this opinion be false, 'tis the most natural of any, and has alone any primary recommendation to the fancy.
As to the second part of the proposition, _that the philosophical system acquires all its influence on the imagination from the vulgar one_; we may observe, that this is a natural and unavoidable consequence of the foregoing conclusion, _that it has no primary recommendation to reason or the imagination_. For as the philosophical system is found by experience to take hold of many minds, and, in particular, of all those who reflect ever so little on this subject, it must derive all its authority from the vulgar system, since it has no original authority of its own. The manner in which these two systems, though directly contrary, are connected together, may be explained as follows.
The imagination naturally runs on in this train of thinking. Our perceptions are our only objects: resembling perceptions are the same, however broken or uninterrupted in their appearance: this appearing interruption is contrary to the identity: the interruption consequently extends not beyond the appearance, and the perception or object really continues to exist, even when absent from us: our sensible perceptions have, therefore, a continued and uninterrupted existence. But as a little reflection destroys this conclusion, that our perceptions have a continued existence, by showing that they have a dependent one, 'twould naturally be expected, that we must altogether reject the opinion, that there is such a thing in nature as a continued existence, which is preserved even when it no longer appears to the senses. The case, however, is otherwise. Philosophers are so far from rejecting the opinion of a continued existence upon rejecting that of the independence and continuance of our sensible perceptions, that though all sects agree in the latter sentiment, the former, which is in a manner its necessary consequence, has been peculiar to a few extravagant sceptics; who, after all, maintained that opinion in words only, and were never able to bring themselves sincerely to believe it.
There is a great difference betwixt such opinions as we form after a calm and profound reflection, and such as we embrace by a kind of instinct or natural impulse, on account of their suitableness and conformity to the mind. If these opinions become contrary, 'tis not difficult to foresee which of them will have the advantage. As long as our attention is bent upon the subject, the philosophical and studied principle may prevail; but the moment we relax our thoughts, nature will display herself, and draw us back to our former opinion. Nay she has sometimes such an influence, that she can stop our progress, even in the midst of our most profound reflections, and keep us from running on with all the consequences of any philosophical opinion. Thus, though we clearly perceive the dependence and interruption of our perceptions, we stop short in our career, and never upon that account reject the notion of an independent and continued existence. That opinion has taken such deep root in the imagination, that 'tis impossible ever to eradicate it, nor will any strained metaphysical conviction of the dependence of our perceptions be sufficient for that purpose.
But though our natural and obvious principles here prevail above our studied reflections, 'tis certain there must be some struggle and opposition in the case; at least so long as these reflections retain any force or vivacity. In order to set ourselves at ease in this particular, we contrive a new hypothesis, which seems to comprehend both these principles of reason and imagination. This hypothesis is the philosophical one of the double existence of perceptions and objects; which pleases our reason, in allowing that our dependent perceptions are interrupted and different, and at the same time is agreeable to the imagination, in attributing a continued existence to something else, which we call _objects_. This philosophical system, therefore, is the monstrous offspring of two principles, which are contrary to each other, which are both at once embraced by the mind, and which are unable mutually to destroy each other. The imagination tells us, that our resembling perceptions have a continued and uninterrupted existence, and are not annihilated by their absence. Reflection tells us, that even our resembling perceptions are interrupted in their existence, and different from each other. The contradiction betwixt these opinions we elude by a new fiction, which is conformable to the hypotheses both of reflection and fancy, by ascribing these contrary qualities to different existences; the _interruption_ to perceptions, and the _continuance_ to objects. Nature is obstinate, and will not quit the field, however strongly attacked by reason; and at the same time reason is so clear in the point, that there is no possibility of disguising her. Not being able to reconcile these two enemies, we endeavour to set ourselves at ease as much as possible, by successively granting to each whatever it demands, and by feigning a double existence, where each may find something that has all the conditions it desires. Were we fully convinced that our resembling perceptions are continued, and identical, and independent, we should never run into this opinion of a double existence; since we should find satisfaction in our first supposition, and would not look beyond. Again, were we fully convinced that our perceptions are dependent, and interrupted, and different, we should be as little inclined to embrace the opinion of a double existence; since in that case we should clearly perceive the error of our first supposition of a continued existence, and would never regard it any farther. 'Tis therefore from the intermediate situation of the mind that this opinion arises, and from such an adherence to these two contrary principles, as makes us seek some pretext to justify our receiving both; which happily at last is found in the system of a double existence.
Another advantage of this philosophical system is its similarity to the vulgar one, by which means we can humour our reason for a moment, when it becomes troublesome and solicitous; and yet upon its least negligence or inattention, can easily return to our vulgar and natural notions. Accordingly we find, that philosophers neglect not this advantage, but, immediately upon leaving their closets, mingle with the rest of mankind in those exploded opinions, that our perceptions are our only objects, and continue identically and uninterruptedly the same in all their interrupted appearances.
There are other particulars of this system, wherein we may remark its dependence on the fancy, in a very conspicuous manner. Of these, I shall observe the two following. _First_, we suppose external objects to resemble internal perceptions. I have already shown, that the relation of cause and effect can never afford us any just conclusion from the existence or qualities of our perceptions to the existence of external continued objects: and I shall farther add, that even though they could afford such a conclusion, we should never have any reason to infer that our objects resemble our perceptions. That opinion, therefore, is derived from nothing but the quality of the fancy above explained, _that it borrows all its ideas from some precedent perception_. We never can conceive any thing but perceptions, and therefore must make every thing resemble them.
Secondly, as we suppose our objects in general to resemble our perceptions, so we take it for granted, that every particular object resembles that perception which it causes. The relation of cause and effect determines us to join the other of resemblance; and the ideas of these existences being already united together in the fancy by the former relation, we naturally add the latter to complete the union.
We have a strong propensity to complete every union by joining new relations to those which we have before observed betwixt any ideas, as we shall have occasion to observe presently.[8] Having thus given an account of all the systems, both popular and philosophical, with regard to external existences, I cannot forbear giving vent to a certain sentiment which arises upon reviewing those systems. I begun this subject with premising, that we ought to have an implicit faith in our senses, and that this would be the conclusion I should draw from the whole of my reasoning. But to be ingenuous, I feel myself _at present_ of a quite contrary sentiment, and am more inclined to repose no faith at all in my senses, or rather imagination, than to place in it such an implicit confidence. I cannot conceive how such trivial qualities of the fancy, conducted by such false suppositions, can ever lead to any solid and rational system. They are the coherence and constancy of our perceptions, which produce the opinion of their continued existence; though these qualities of perceptions have no perceivable connexion with such an existence. The constancy of our perceptions has the most considerable effect, and yet is attended with the greatest difficulties. 'Tis a gross illusion to suppose, that our resembling perceptions are numerically the same; and 'tis this illusion which leads us into the opinion, that these perceptions are uninterrupted, and are still existent, even when they are not present to the senses. This is the case with our popular system. And as to our philosophical one, 'tis liable to the same difficulties; and is, over and above, loaded with this absurdity, that it at once denies and establishes the vulgar supposition. Philosophers deny our resembling perceptions to be identically the same, and uninterrupted; and yet have so great a propensity to believe them such, that they arbitrarily invent a new set of perceptions, to which they attribute these qualities. I say, a new set of perceptions: for we may well suppose in general, but 'tis impossible for us distinctly to conceive, objects to be in their nature any thing but exactly the same with perceptions.
What then can we look for from this confusion of groundless and extraordinary opinions but error and falsehood? And how can we justify to ourselves any belief we repose in them?
This sceptical doubt, both with respect to reason and the senses, is a malady which can never be radically cured, but must return upon us every moment, however we may chase it away, and sometimes may seem entirely free from it. 'Tis impossible, upon any system, to defend either our understanding or senses; and we but expose them farther when we endeavour to justify them in that manner. As the sceptical doubt arises naturally from a profound and intense reflection on those subjects, it always increases the farther we carry our reflections, whether in opposition or conformity to it. Carelessness and inattention alone can afford us any remedy. For this reason I rely entirely upon them; and take it for granted, whatever may be the reader's opinion at this present moment, that an hour hence he will be persuaded there is both an external and internal world; and, going upon that supposition, I intend to examine some general systems, both ancient and modern, which have been proposed of both, before I proceed to a more particular inquiry concerning our impressions. This will not, perhaps, in the end, be found foreign to our present purpose.
[1] Part II. Sect. 6.
[2] Sect. 5.
[3] Part II. Sect. 4.
[4] Part II. Sect. 5.
[5] Part. II. Sect. 5.
[6] This reasoning, it must be confessed, is somewhat abstruse, and difficult to be comprehended; but it is remarkable, that this very difficulty may be converted into a proof of the reasoning. We may observe, that there are two relations, and both of them resemblances, which contribute to our mistaking the succession of our interrupted perceptions for an identical object. The first is, the resemblance of the perceptions: the second is, the resemblance which the act of the mind in surveying a succession of resembling objects, bears to that in surveying an identical object. Now these resemblances we are apt to confound with each other; and 'tis natural we should, according to this very reasoning. But let us keep them distinct, and we shall find no difficulty in conceiving the precedent argument.
[7] Sect. 6.
[8] Sect. 5.
SECTION III.
OF THE ANCIENT PHILOSOPHY.
Several moralists have recommended it as an excellent method of becoming acquainted with our own hearts, and knowing our progress in virtue, to recollect our dreams in a morning, and examine them with the same rigour that we would our most serious and most deliberate actions.
Our character is the same throughout, say they, and appears best where artifice, fear and policy, have no place, and men can neither be hypocrites with themselves nor others. The generosity or baseness of our temper, our meekness or cruelty, our courage or pusillanimity, influence the fictions of the imagination with the most unbounded liberty, and discover themselves in the most glaring colours. In like manner, I am persuaded, there might be several useful discoveries made from a criticism of the fictions of the ancient philosophy concerning _substances, and substantial forms, and accidents, and occult qualities_, which, however unreasonable and capricious, have a very intimate connexion with the principles of human nature.
'Tis confessed by the most judicious philosophers, that our ideas of bodies are nothing but collections formed by the mind of the ideas of the several distinct sensible qualities, of which objects are composed, and which we find to have a constant union with each other. But however these qualities may in themselves be entirely distinct, 'tis certain we commonly regard the compound, which they form, as _one_ thing, and as continuing the _same_ under very considerable alterations.
The acknowledged composition is evidently contrary to this supposed _simplicity_, and the variation to the _identity_. It may therefore be worth while to consider the _causes_, which make us almost universally fall into such evident contradictions, as well as the _means_ by which we endeavour to conceal them.
'Tis evident, that as the ideas of the several distinct _successive_ qualities of objects are united together by a very close relation, the mind, in looking along the succession, must be carried from one part of it to another by an easy transition, and will no more perceive the change, than if it contemplated the same unchangeable object. This easy transition is the effect, or rather essence of relation; and as the imagination readily takes one idea for another, where their influence on the mind is similar; hence it proceeds, that any such succession of related qualities is readily considered as one continued object, existing without any variation. The smooth and uninterrupted progress of the thought, being alike in both cases, readily deceives the mind, and makes us ascribe an identity to the changeable succession of connected qualities.
But when we alter our method of considering the succession, and, instead of tracing it gradually through the successive points of time, survey at once any two distinct periods of its duration, and compare the different conditions of the successive qualities; in that case the variations, which were insensible when they arose gradually, do now appear of consequence, and seem entirely to destroy the identity.
By this means there arises a kind of contrariety in our method of thinking, from the different points of view, in which we survey the object, and from the nearness or remoteness of those instants of time, which we compare together. When we gradually follow an object in its successive changes, the smooth progress of the thought makes us ascribe an identity to the succession; because 'tis by a similar act of the mind we consider an unchangeable object. When we compare its situation after a considerable change the progress of the thought is broke; and consequently we are presented with the idea of diversity; in order to reconcile which contradictions the imagination is apt to feign something unknown and invisible, which it supposes to continue the same under all these variations; and this unintelligible something it calls a _substance, or original and first matter_.
We entertain a like notion with regard to the _simplicity_ of substances, and from like causes. Suppose an object perfectly simple and indivisible to be presented, along with another object, whose _co-existent_ parts are connected together by a strong relation, 'tis evident the actions of the mind, in considering these two objects, are not very different. The imagination conceives the simple object at once, with facility, by a single effort of thought, without change or variation. The connexion of parts in the compound object has almost the same effect, and so unites the object within itself, that the fancy feels not the transition in passing from one part to another. Hence the colour, taste, figure, solidity, and other qualities, combined in a peach or melon, are conceived to form _one thing_; and that on account of their close relation, which makes them affect the thought in the same manner, as if perfectly uncompounded. But the mind rests not here.
Whenever it views the object in another light, it finds that all these qualities are different, and distinguishable, and separable from each other; which view of things being destructive of its primary and more natural notions, obliges the imagination to feign an unknown something, or _original_ substance and matter, as a principle of union or cohesion among these qualities, and as what may give the compound object a title to be called one thing, notwithstanding its diversity and composition.
The Peripatetic philosophy asserts the _original_ matter to be perfectly homogeneous in all bodies, and considers fire, water, earth, and air, as of the very same substance, on account of their gradual revolutions and changes into each other. At the same time it assigns to each of these species of objects a distinct _substantial form_, which it supposes to be the source of all those different qualities they possess, and to be a new foundation of simplicity and identity to each particular species. All depends on our manner of viewing the objects.
When we look along the insensible changes of bodies, we suppose all of them to be of the same substance or essence. When we consider their sensible differences, we attribute to each of them a substantial and essential difference. And in order to indulge ourselves in both these ways of considering our objects, we suppose all bodies to have at once a substance and a substantial form.
The notion of _accidents_ is an unavoidable consequence of this method of thinking with regard to substances and substantial forms; nor can we forbear looking upon colours, sounds, tastes, figures, and other properties of bodies, as existences, which cannot subsist apart, but require a subject of inhesion to sustain and support them. For having never discovered any of these sensible qualities, where, for the reasons above mentioned, we did not likewise fancy a substance to exist; the same habit, which makes us infer a connexion betwixt cause and effect, makes us here infer a dependence of every quality on the unknown substance. The custom of imagining a dependence has the same effect as the custom of observing it would have. This conceit, however, is no more reasonable than any of the foregoing. Every quality being a distinct thing from another, may be conceived to exist apart, and may exist apart not only from every other quality, but from that unintelligible chimera of a substance.
But these philosophers carry their fictions still farther in their sentiments concerning _occult qualities_, and both suppose a substance supporting, which they do not understand, and an accident supported, of which they have as imperfect an idea. The whole system, therefore, is entirely incomprehensible, and yet is derived from principles as natural as any of these above explained.
In considering this subject, we may observe a gradation of three opinions that rise above each other, according as the persons who form them acquire new degrees of reason and knowledge. These opinions are that of the vulgar, that of a false philosophy, and that of the true; where we shall find upon inquiry, that the true philosophy approaches nearer to the sentiments of the vulgar than to those of a mistaken knowledge. 'Tis natural for men, in their common and careless way of thinking, to imagine they perceive a connexion betwixt such objects as they have constantly found united together; and because custom has rendered it difficult to separate the ideas, they are apt to fancy such a separation to be in itself impossible and absurd. But philosophers, who abstract from the effects of custom, and compare the ideas of objects, immediately perceive the falsehood of these vulgar sentiments, and discover that there is no known connexion among objects. Every different object appears to them entirely distinct and separate; and they perceive that 'tis not from a view of the nature and qualities of objects we infer one from another, but only when in several instances we observe them to have been constantly conjoined.
But these philosophers, instead of drawing a just inference from this observation, and concluding, that we have no idea of power or agency, separate from the mind and belonging to causes; I say, instead of drawing this conclusion, they frequently search for the qualities in which this agency consists, and are displeased with every system which their reason suggests to them, in order to explain it. They have sufficient force of genius to free them from the vulgar error, that there is a natural and perceivable connexion betwixt the several sensible qualities and actions of matter, but not sufficient to keep them from ever seeking for this connexion in matter or causes. Had they fallen upon the just conclusion, they would have returned back to the situation of the vulgar, and would have regarded all these disquisitions with indolence and indifference. At present they seem to be in a very lamentable condition, and such as the poets have given us but a faint notion of in their descriptions of the punishment of Sisyphus and Tantalus. For what can be imagined more tormenting than to seek with eagerness what for ever flies us, and seek for it in a place where 'tis impossible it can ever exist?
But as Nature seems to have observed a kind of justice and compensation in every thing, she has not neglected philosophers more than the rest of the creation, but has reserved them a consolation amid all their disappointments and afflictions. This consolation principally consists in their invention of the words _faculty_ and _occult quality_. For it being usual, after the frequent use of terms, which are really significant and intelligible, to omit the idea which we would express by them, and preserve only the custom by which we recal the idea at pleasure; so it naturally happens, that after the frequent use of terms which are wholly insignificant and unintelligible, we fancy them to be on the same footing with the precedent, and to have a secret meaning which we might discover by reflection. The resemblance of their appearance deceives the mind, as is usual, and makes us imagine a thorough resemblance and conformity. By this means these philosophers set themselves at ease, and arrive at last, by an illusion, at the same indifference which the people attain by their stupidity, and true philosophers by their moderate scepticism. They need only say, that any phenomenon which puzzles them arises from a faculty or an occult quality, and there is an end of all dispute and inquiry upon the matter.
But among all the instances wherein the Peripatetics have shown they were guided by every trivial propensity of the imagination, no one is more remarkable than their _sympathies, antipathies, and horrors of a vacuum_. There is a very remarkable inclination in human nature to bestow on external objects the same emotions which it observes in itself, and to find every where those ideas which are most present to it. This inclination, 'tis true, is suppressed by a little reflection, and only takes place in children, poets, and the ancient philosophers.
It appears in children, by their desire of beating the stones which hurt them: in poets by their readiness to personify every thing; and in the ancient philosophers, by these fictions of sympathy and antipathy.
We must pardon children, because of their age; poets, because they profess to follow implicitly the suggestions of their fancy; but what excuse shall we find to justify our philosophers in so signal a weakness?
SECTION IV.
OF THE MODERN PHILOSOPHY.
But here it may be objected, that the imagination, according to my own confession, being the ultimate judge of all systems of philosophy, I am unjust in blaming the ancient philosophers for making use of that faculty, and allowing themselves to be entirely guided by it in their reasonings. In order to justify myself, I must distinguish in the imagination betwixt the principles which are permanent, irresistible, and universal; such as the customary transition from causes to effects, and from effects to causes: and the principles, which are changeable, weak and irregular; such as those I have just now taken notice of. The former are the foundation of all our thoughts and actions, so that upon their removal, human nature must immediately perish and go to ruin. The latter are neither unavoidable to mankind, nor necessary, or so much as useful in the conduct of life; but, on the contrary, are observed only to take place in weak minds, and being opposite to the other principles of custom and reasoning, may easily be subverted by a due contrast and opposition. For this reason, the former are received by philosophy, and the latter rejected. One who concludes somebody to be near him, when he hears an articulate voice in the dark, reasons justly and naturally; though that conclusion be derived from nothing but custom, which infixes and enlivens the idea of a human creature, on account of his usual conjunction with the present impression. But one, who is tormented he knows not why, with the apprehension of spectres in the dark, may perhaps be said to reason, and to reason naturally too: but then it must be in the same sense that a malady is said to be natural; as arising from natural causes, though it be contrary to health, the most agreeable and most natural situation of man.
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 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 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.