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CHAPTER V.

Demonstrative Reasoning, and Intuitive Certainty.

Passing from the shadowy regions of conjecture and probability, we next come to those which are illuminated by a clear and full light. As experimental philosophy, which we nave admitted, can never amount to absolute demonstration, although, sometimes furnishing an evidence entirely sufficient to satisfy the mind, rests upon our sensitive knowledge, or that knowledge which is derived to us through the senses, so all demonstrative certainty rests ultimately upon intui. tion. By intuition is meant, that act of the mind by which it perceives the truth of any proposition, as soon as it is propounded, without exertion or examination. It may, I think, be justly regarded as the simplest effort of reason, the great power with which we are endowed by our Creator, for the search and discovery of truth. In matters of experimental knowledge, reason has to derive its materials from experience and observation, and on them alone to ground its conclusions; in matters of demonstration and entire certainty, it grounds them upon intuitive evidence, and its office is to trace the connection of our ideas, or what is the same thing, the habitudes, correspondences, and relations of things. Things equal to the same thing, are equal to one another: if from equal quantities the same quantity be taken, the remainders will be equal. These are said to be intuitive truths, or axioms, because they are at once perceived by the mind, by a single glance of attention, and flash with a light upon it that is irresistible. This world must be the workmanship of a Divine Contriver; men are accountable to their Creator for their conduct. These are truths also perfectly certain; but, although susceptible of complete proof, their evidence does not so instantaneously force conviction upon the mind, as in the cases before mentioned. They are, on this account, denominated demonstrable truths. The mind has to exert itself, and go in quest of intuitive truths, by which to prove them. The perception of intuitive truths, therefore, may be justly regarded as the first and simplest exercise of reason, while its more complex acts consist in searching out things, that are unknown from those that are known. The most certain of all those truths, with which the human mind is conversant, are those that are intuitive. In tracing this kind of truth, it is, as it appears to me, that the methods of analysis and synthesis, have place in the greatest propriety of language. I know that the greatest philosophers have appropriated the terms also to other branches of science, and others, who have followed them in this track, have not always nicely discriminated between the two modes of investigation, but have used the terms with great confusion and ambiguity, some making that to be the synthetical method, which others have resolved into the analytical. Newton, in his Opticks, as quoted by Dr. Johnson in his Dictionary, defines the “ analysis to consist in making experiments and observations, and in drawing general conclusions from them by induction, and admitting of no objections, but such as are taken from experiments or other certain truths.” The same author makes synthesis to consist in assuming the causes discovered and established as principles, and by them explaining the phenomena proceeding from them, and proving the explanations. According to this illustrious man, then, while we are engaged in the pursuit of science, or the causes of things, by experiment and observation, or what Bacon, as we before showed, calls his axiomata generalia, general maxims, we are following the analytical method; but when we come to assume those causes or general truths, as already ascertained, and undertake to apply them to the solution of other phenomena, we are pursuing the synthetical. This distinction is intelligible, although not exactly suited to the original meaning of the terms, and in its application to practice, likely to give rise to great ambiguity and uncertainty. It will readily be perceived, also, by those who have taken the pains to enter into the full import and extent of lord Bacon's method of induction, that both the analytical and synthetical method, as thus represented by Newton, are included in it. It implies both a full and complete collection of facts by experiment and observation, drawing conclusions from them; and then finally, the application of the principles thus ascertained, to other facts that may arise. To explain the matter by an example-Franklin was, according to Newton, pursuing the analytical method, while making experiments in electricity, by which he discovered, first, the existence of the electric fluid, then its identity with lightning: and he was following the synthetical, when, having proved the existence of such a cause, he explained the phenomena of lightning, meteors, the Aurora Borealis, &c. Perhaps, however, it would serve to give more clearness to our conceptions, and relieve us from all ambiguity in the use of words, than which nothing can be of more importance in philosophy, if the whole of that process of investigation, by which we become the interpreters of nature, or make discoveries in the moral and physical world, should be denominated induction; while the terms analysis and synthesis, are limited to signify those methods, by which we trace the relations of things, and the necessary connexion of our ideas. Analysis, as the etymology of the term indicates, implies the decomposition or loosening asunder, of that which is compound into its simple elements, while synthesis, as its derivation also denotes, expresses directly the contrary process, viz. the composition of what is very complex, out of a number of simple ingredients. In taking my watch to pieces, and exposing to view the parts of which it is composed in regular succession, I follow the method of analy. sis; when, on the other hand, I put all its parts together again, and after adjusting them in their places, form them into a complete time-piece, I pursue the method of synthesis. When complex truths, therefore, are resolved into those simple ones, of which they are composed, it is the analytical mode of procedure; but when we advance from the simple to the complex, the synthetical.

In this part of knowledge, it is, if any where, that we should expect the syllogistic art to become useful, in tracing the necessary connexion of our ideas, and the immutable habitudes and relations of things. In the experimental sciences, it is evidently futile, and even positively injurious, as it is apt to lead us too precipitately and incautiously, to establish general principles. In the language of Bacon, in his novum organum; sicut scientiæ quæ nunc habenter, inutiles sunt ad inventionem operum, ita logica qùæ nunc habetur, inutilis est ad inventionem scientiarum. Logica quæ in usu est ad errores stabiliendos et figendos valet, potius quam ad inquisitionem veritatis; ut magis damnosa sit quam utilis. Syllogismus ad principia scientiarum non adhibetur, ad me. dia axiomata frustra adhibetur, cum sit subtilitate naturæ longe impar; assensum itaque constringit non res. After the truth has been ascertained, a syllogism may serve to place it in such an undeniable form, as shall preclude the possibility of doubting it, and silence gainsayers and sceptics; but in that effort of understanding by which truth is investigated, it cannot prove of the smallest advantage, and in fact has nothing to do. Syllogism is intended by its author and his followers, to become an aid to reason, but of what advantage can we imagine were syllogisms to Newton, in his discovery of the theory of gravitation, or Harvey in tracin the circulation of the blood? One of the greatest faults of

Aristotle, is, his continued attempt to apply the rules of this art, even in his natural and moral researches, and this circumstance gives to his deepest inquiries on those topics, the air of a frivolous and quibbling logic. Primi generis, says Bacon, exemplum in Aristotele maximè conspicuum est, qui philosophiam naturalem dialectica sua corrupit.

It is evident, therefore, that in the pursuits of natural philosophy, in all its branches, whether relative to matter or mind, all of which are admitted to rest only upon probability, and where some suspense of judgment is presupposed, while we are engaged in the prosecution of facts, the art of syllogising is worse than useless, it is absolutely pernicious. It may assist us in dogmatising, but can furnish no aid towards a solution of the phenomena of nature. Nor can it be more useful in those branches of learning, whose province it is to trace the agreement or disagreement of our ideas, or to establish immutable and eternal truths. If there be supposed to be any power or force in a syllogism, as an auxiliary to reason, it lends its reinforcement at too late a period of our contest with truth, to contribute in any degree to our victory. Reason has obtained the mastery, and traced the connexion of ideas, or arrived at the conclusion, before the syllogism furnishes her its support. Take the simplest example that can be conceived, in order to test the force of the syllogistic art, with which learned Sorbonnists have made such a pother in the world; and by the adroit use of which, like expert fencers, they could attack, repel, make and parry strokes, and after they were foiled or completely vanquished, still maintain the contest with zeal unabated, and with chivalry undaunted. Suppose, for example, in the case usually enunciated in the received systems of logic, that we wish to trace the connection between man and accountableness, or determine whether man be accountable for his actions. Here the mind sets itself to work, to discover what those considerations are, which render a being such as man

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