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The foregoing critical remarks will, I hope, have their use in keeping this distinction more steadily in the view of future inquirers; and in preventing some of the readers of the publications to which they relate, from conceiving a prejudice, in consequence of the looseness of that phraseology which has been accidentally adopted by their authors, against the just and important conclusions which they contain.
of his own, and has even spoken of this meaning as a thing not generally understood. Thus, after illustrating the different classes of natural signs, he adds the following sentence: “ It may be observed, that as the first class of natural signs I have mentioned is the foundation of true philosophy, and the second of the fine arts or of taste, so the last is the foundation of common sense; a part of human nature which hath never been explained." Inquiry, Chap. v. sect. 3.
See Note (D.)
OF REASONING AND OF DEDUCTIVE EVIDENCE.
Doubts with respect to Locke's Distinction between the
Powers of Intuition and of Reasoning.
ALTHOUGH, in treating of this branch of the Philosophy of the Mind, I have followed the example of preceding writers, so far as to speak of intuition and reasoning as two different faculties of the understanding, I am by no means satisfied that there exists between them that radical distinction which is commonly apprehended. Dr. Beattie, in his Essay on Truth, has attempted to show, that, how closely soever they may in general be connected, yet that this connexion is not necessary; insomuch, that a being may be conceived endued with the one, and at the same time destitute of the other. * Something of this kind, he remarks, takes place in dreams and in madness; in both of which states of the system, the power of reasoning appears occasionally to be retained in no inconsiderable degree, while the power of intuition is suspended or lost. But this doctrine is lia
Beattie's Essay, p. 41, 2d edit.
ble to obvious, and to insurmountable objections; and has plainly taken its rise from the vagueness of the phrase common sense, which the author employs through the whole of his argument, as synonymous with the power of intuition. Of the indissoluble connexion between this last power and that of reasoning, no other proof is necessary than the following consideration, that, “ in every step which reason makes in demonstrative knowledge, there must be intuitive certainty;" a proposition which Locke has excellently illustrated, and which, since his time, has been acquiesced in, so far as I know, by philosophers of all descriptions. From this proposition (which, when properly interpreted, appears to me to be perfectly just) it obviously follows, that the power of reasoning presupposes the power of intuition; and, therefore, the only question about which any doubt can be entertained is, Whether the power of intuition (according to Locke's idea of it) does not also imply that of reasoning? My own opinion is, decidedly, that it does; at least, when combined with the faculty of memory. In examining those processes of thought which conduct the mind by a series of consequences from premises to a conclusion, I can detect no intellectual act whatever, which the joint operation of intuition and of memory does not sufficiently explain.
Before, however, proceeding farther in this discussion, it is proper for me to observe, by way of comment on the proposition just quoted from Locke, that, although, “ in a complete demonstration, there must be intuitive evidence at every step,” it is not to be supposed, that, in every demonstration, all the various intuitive judgments
leading to the conclusion are actually presented to our thoughts. In by far the greater number of instances, we trust entirely to judgments resting upon the evidence of memory; by the help of which faculty, we are enabled to connect together the most remote truths, with the very same confidence as if the one were an immediate consequence of the other. Nor does this diminish, in the smallest degree, the satisfaction we feel in following such a train of reasoning. On the contrary, nothing can be more disgusting than a demonstration where even the simplest and most obvious steps are brought forward to view; and where no appeal is made to that stock of previous knowledge which memory has identified with the operations of reason. Still, however, it is true, that it is by a continued chain of intuitive judgments, that the whole science of geometry hangs together; inasmuch as the demonstration of any one proposition virtually includes all the previous demonstrations to which it refers.
Hence it appears, that, in mathematical demonstrations, we have not, at every step, the immediate evidence of intuition, but only the evidence of memory. Every demonstration, however, may be resolved into a series of separate judgments, either formed at the moment, or remembered as the results of judgments formed at some preceding period; and it is in the arrangement and concatenation of these different judgments, or media of proof, that the inventive and reasoning powers of the mathematician find so noble a field for their exercise.
With respect to these powers of judgment and of reasoning, as they are here combined, it appears to me, that
the results of the former may be compared to a collection of separate stones prepared by the chisel for the purposes of the builder; upon each of which stones, while lying on the ground, a person may raise himself, as upon a pedestal, to a small elevation. The same judgments, when combined into a train of reasoning, terminating in a remote conclusion, resemble the formerly unconnected blocks, when converted into the steps of a staircase leading to the summit of a tower, which would be otherwise inaccessible. In the design and execution of this staircase, much skill and invention may be displayed by the architect; but, in order to ascend it, nothing more is necessary than a repetition of the act by which the first step was gained. The fact I conceive to be somewhat analogous, in the relation between the power of judgment, and what logicians call the discursive processes of the understanding
Mr. Locke's language, in various parts of his Essay, seems to accord with the same opinion. “Every step in reasoning, (he observes) that produces knowledge, has intuitive certainty ; which, when the mind perceives, there is no more required but to remember it, to make the agreement or disagreement of the ideas, concerning which we inquire, visible and certain. This intuitive perception of the agreement or disagreement of the intermediate ideas, in each step and progression of the demonstration, must also be carried exactly in the mind, and a man must be sure that no part is left out; which, in long deductions, and in the use of many proofs, the memory does not always so readily and exactly retain: therefore it comes to pass, that this is more imperfect than intuitive know