Lectures on the Philosophy of the Human Mind (Vol. 1 of 3). Brown Thomas
as far as he was able, from past experience, what the circumstances would have been, in every respect, if the cause supposed had been actually present; and, even if these were all found to be exactly coincident, though he would think the presence of the cause more probable, he would be very far from considering it as certain, and would still endeavour to lessen the chances of fallacy, by watching the circumstances, should they again recur, and varying them, by experiment, in every possible way.
This patience and caution, however, essential as they are to just philosophizing, require, it must be confessed, no slight efforts of self-denial, but of a self-denial which is as necessary to intellectual excellence as the various moral species of self-denial are to excellence and virtue.
“Mr Locke, I think,” says Dr Reid, “mentions an eminent musician, who believed that God created the world in six days, and rested the seventh, because there are but seven notes in music. I myself,” he continues, “knew one of that profession, who thought that there could be only three parts in harmony, to wit, bass, tenor, and treble; because there are but three persons in the Trinity.”30
The minds that could be satisfied with analogies so very slight, must, indeed, have been little acquainted with the principles of philosophic inquiry; and yet how many systems have been advanced in different ages, admired by multitudes, who knew them only by name, and still more revered by the philosophers, who gloried in adopting them, that have been founded on analogies almost as slight.
“The philosophers who form hypothetical systems of the universe, and of all its most secret laws,” says Voltaire, in one of his lively similes, “are like our travellers that go to Constantinople, and think that they must tell us a great deal about the seraglio. They pretend to know every thing which passes within it – the whole secret history of the Sultan and his favourites, and they have seen nothing but its outside walls.”
In one respect, however, philosophers, in their hypothetical systems, far outdo the travellers to Constantinople. They not merely tell us secrets of nature, which they have no opportunity of learning, but they believe the very tales of their own fancy. To see any usual phenomenon, is, indeed, to wonder at it, at first; but to explain it, is almost the very next step, reason serving rather to defend the explanation, when it is made, than to assist greatly in making it; and, in many cases, each philosopher has his separate explanation, on which he is disposed to put as much reliance, as on the certainty of the fact itself, not abandoning the hypothesis, even though the fact should prove to have been different, but making it bend, with a happy pliability, to all the diversities discovered, so as at last, perhaps, to account for circumstances the very reverse of those which it was originally invented to explain. “I have heard,” says Condillac, “of a philosopher, who had the happiness of thinking that he had discovered a principle, which was to explain all the wonderful phenomena of chemistry; and who, in the ardour of his self-congratulation, hastened to communicate his discovery to a skilful chemist. The chemist had the kindness to listen to him, and then calmly told him, that there was but one unfortunate circumstance for his discovery, which was, that the chemical facts were exactly the reverse of what he had supposed. Well then, said the philosopher, have the goodness to tell me what they are, that I may explain them by my system.”31 To those who know that fondness for conjecture, which may almost be said to be a sort of intellectual appetite, there is nothing in all the wonders which Swift tells us of his fabled Houynhnhms, that marks them more strongly as a different race from mankind, than the total absence of hypothesis from their systems of knowledge.
“I remember,” says Gulliver, “it was with extreme difficulty that I could bring my master to understand the meaning of the word opinion, or how a point could be disputable; because reason taught us to affirm or deny only when we are certain; and beyond our knowledge we cannot do either. So that controversies, wranglings, disputes, and positiveness, in false or dubious propositions, are evils unknown among the Houynhnhms. In the like manner, when I used to explain to him our several systems of Natural Philosophy, he would laugh, that a creature pretending to reason, should value itself upon the knowledge of other people's conjectures, and in things, where that knowledge, if it were certain, could be of no use. Wherein he agreed entirely with the sentiments of Socrates, as Plato delivers them, which I mention as the highest honour I can do that Prince of philosophers. I have often since reflected what destruction such a doctrine would make in the libraries of Europe, and how many paths to fame would be then shut up in the learned world.”32
While I wish to caution you against a fondness for hypotheses, by shewing you, not merely that they are liable to error, – for inquiry, of every kind, must be so in some degree, – but that, in truth, they leave the real difficulty of the succession of the observed consequents to the observed antecedents as great as before, and only add, to the supposed difficulty of explaining one sequence, the necessity of explaining a sequence additional, – I must remark, at the same time, that what is commonly termed theory, in opposition to hypothesis, is far from being so different from it as is commonly represented, – at least, in the very wide application which is usually made of it. We are told, by those who lay down rules of philosophizing, that the object of philosophy is, to observe particulars, and, from these, to frame general laws, which may, again, be applied to the explanation of particulars; and the view which is thus given of the real province of philosophy is undoubtedly a just one; – but there is an ambiguity in the language which may deceive you, and with respect to which, therefore, it is necessary for you to be on your guard. If, by the term general law, be meant the agreement in some common circumstances of a number of events observed, there can be no question that we proceed safely in framing it, and that what we have already found in a number of events, must be applicable to that number of events; in the same manner, as, after combining in the term animal the circumstances in which a dog, a horse, a sheep agree, we cannot err in applying the term animal to a dog, a horse, a sheep. But the only particular to which, in this case, we can, with perfect confidence, apply a general law, are the very particulars that have been before observed by us. If it be understood as more general than the circumstances observed, and, therefore, capable of being applied with perfect certainty to the explanation of new phenomena, we evidently, to the extent in which the general law is applied beyond the circumstances observed, proceed on mere supposition, as truly, as in any hypothesis which we could have framed; and though the supposition may be more and more certain, in proportion to the number of cases thus generalized, and the absence of any circumstance which can be supposed, in the new case, to be inconsistent with it, it never can amount to actual certainty. Let us take, for example, one of the most striking cases of this sort. That bodies tend to each other, in all circumstances, with a force increasing directly as their quantities, and inversely as the squares of their distances, may seem in the highest degree probable indeed, from the innumerable facts observed on our globe, and in the magnificent extent of the planetary movements; but it cannot be said to be certain at all distances, in which we have never had an opportunity of making observations, – as it seems to be verified in the heights of our atmosphere, and in the distances of the planets, in their orbits, from the sun, and from each other. It is not necessary, however, to refer, for possible exceptions, to spaces that are beyond our observation; since, on the surface of our own earth, there is abundant evidence, that the law does not hold universally. Every quiescent mass that is capable of greater compression, and of which the particles, therefore, before that compression, are not in absolute contact, shews sufficiently, that the principle of attraction, which, of itself, would have brought them into actual contact, must have ceased to operate, while there was still a space between the particles that would have allowed its free operation; and, in the phenomena of elasticity, and impulse in general, it has not merely ceased, but is actually reversed, – the bodies which, at all visible distances, exhibited a reciprocal attraction, now exhibiting a reciprocal repulsion, in consequence of which they mutually fly off, as readily as they before approached, – that is to say, the tendency of bodies to each other being converted into a tendency from each other, by a mere change of distance, so slight as to be almost inappreciable. When a ball rebounds from the earth, toward which it moved rapidly before, and the gravitating tendency is thus evidently reversed, without the intervention of any foreign force, what
On the Powers of the Human Mind, Essay vi. Chap. viii. Vol. II. p. 334. 8vo.
Traite des Systemes, chap. xii. Vol. II. p. 372.
Travels, Part iv, chap. 8. Swift's Works,