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For with what confidence can I venture upon such bold enterprises, when, beside those numberless infirmities peculiar to myself, I find so many which are common to human nature? Can I be sure that, in leaving all established opinions, I am following truth? and by what criterion shall I distinguish her, even if fortune should at last guide me on her footsteps? After the most accurate and exact of my reasonings, I can give no reason why I should assent to it, and feel nothing but a strong propensity to consider objects strongly in that view under which they appear to me. Experience is a principle which instructs me in the several conjunctions of objects for the past. Habit is another principle which determines me to expect the same for the future; and both of them conspiring to operate upon the imagination, make me form certain ideas in a more intense and lively manner than others which are not attended with the same advantages. Without this quality, by which the mind enlivens some ideas beyond others (which seemingly is so trivial, and so little founded on reason), we could never assent to any argument, nor carry our view beyond those few objects which are present to our senses. Nay, even to these objects we could never attribute any existence but what was dependent on the senses, and must comprehend them entirely in that succession of perceptions which constitutes our self or person. Nay, farther, even with relation to that succession, we could only admit of those perceptions which are immediately present to our consciousness; nor could those lively images, with which the memory presents us, be ever received as true pictures of past perceptions. The memory, senses, and understanding[Pg 337] are therefore all of them founded on the imagination, or the vivacity of our ideas.

No wonder a principle so inconstant and fallacious should lead us into errors when implicitly followed (as it must be) in all its variations. 'Tis this principle which makes us reason from causes and effects; and 'tis the same principle which convinces us of the continued existence of external objects when absent from the senses. But though these two operations be equally natural and necessary in the human mind, yet in some circumstances they are directly contrary;[17] nor is it possible for us to reason justly and regularly from causes and effects, and at the same time believe the continued existence of matter. How then shall we adjust those principles together? Which of them shall we prefer? Or in case we prefer neither of them, but successively assent to both, as is usual among philosophers, with what confidence can we afterwards usurp that glorious title, when we thus knowingly embrace a manifest contradiction?

This contradiction[18] would be more excusable were it compensated by any degree of solidity and satisfaction in the other parts of our reasoning. But the case is quite contrary. When we trace up the human understanding to its first principles, we find it to lead us into such sentiments as seem to turn into ridicule all our past pains and industry, and to discourage us from future inquiries. Nothing is more curiously inquired after by the mind of man than the causes of every phenomenon; nor are we content with knowing the immediate causes, but push on our inquiries till we arrive[Pg 338] at the original and ultimate principle. We would not willingly stop before we are acquainted with that energy in the cause by which it operates on its effect; that tie, which connects them together; and that efficacious quality on which the tie depends. This is our aim in all our studies and reflections: and how must we be disappointed when we learn that this connexion, tie, or energy lies merely in ourselves, and is nothing but that determination of the mind which is acquired by custom, and causes us to make a transition from an object to its usual attendant, and from the impression of one to the lively idea of the other? Such a discovery not only cuts off all hope of ever attaining satisfaction, but even prevents our very wishes; since it appears, that when we say we desire to know the ultimate and operating principle as something which resides in the external object, we either contradict ourselves, or talk without a meaning.

This deficiency in our ideas is not indeed perceived in common life, nor are we sensible that, in the most usual conjunctions of cause and effect, we are as ignorant of the ultimate principle which binds them together, as in the most unusual and extraordinary. But this proceeds merely from an illusion of the imagination; and the question is, how far we ought to yield to these illusions. This question is very difficult, and reduces us to a very dangerous dilemma, whichever way we answer it. For if we assent to every trivial suggestion of the fancy, beside that these suggestions are often contrary to each other, they lead us into such errors, absurdities, and obscurities, that we must at last become ashamed of our credulity. Nothing is more dangerous to reason than the flights of the imagination,[Pg 339] and nothing has been the occasion of more mistakes among philosophers. Men of bright fancies may in this respect be compared to those angels, whom the Scripture represents as covering their eyes with their wings. This has already appeared in so many instances, that we may spare ourselves the trouble of enlarging upon it any farther.

But, on the other hand, if the consideration of these instances makes us take a resolution to reject all the trivial suggestions of the fancy, and adhere to the understanding, that is, to the general and more established properties of the imagination; even this resolution, if steadily executed, would be dangerous, and attended with the most fatal consequences. For I have already shown,[19] that the understanding, when it acts alone, and according to its most general principles, entirely subverts itself, and leaves not the lowest degree of evidence in any proposition, either in philosophy or common life. We save ourselves from this total scepticism only by means of that singular and seemingly trivial property of the fancy, by which we enter with difficulty into remote views of things, and are not able to accompany them with so sensible an impression, as we do those which are more easy and natural. Shall we, then, establish it for a general maxim, that no refined or elaborate reasoning is ever to be received? Consider well the consequences of such a principle. By this means you cut off entirely all science and philosophy: you proceed upon one singular quality of the imagination, and by a parity of reason must embrace all of them: and you expressly contradict yourself;[Pg 340] since this maxim must be built on the preceding reasoning, which will be allowed to be sufficiently refined and metaphysical. What party, then, shall we choose among these difficulties? If we embrace this principle, and condemn all refined reasoning, we run into the most manifest absurdities. If we reject it in favour of these reasonings, we subvert entirely the human understanding. We have therefore no choice left, but betwixt a false reason and none at all. For my part, I know not what ought to be done in the present case. I can only observe what is commonly done; which is, that this difficulty is seldom or never thought of; and even where it has once been present to the mind, is quickly forgot, and leaves but a small impression behind it. Very refined reflections have little or no influence upon us; and yet we do not, and cannot establish it for a rule, that they ought not to have any influence; which implies a manifest contradiction.