of knowledge; and, as such, it necessarily lacks the precision and the demonstrative certainty which are characteristic of the principles of Pure Logic. The Laws of Pure Thought are absolute; the merits of Perfect Thought are various, and attainable in different degrees, "according to circumstances.

as

Another distinction has been taken, in this science, between Pure and Applied Logic, or, as Sir William Hamilton prefers to call the latter, Modified Logic. The former, as we have seen, considers the Thinking Faculty alone, as if it constituted the whole of the human mind, and therefore as if its Laws and Products were unaffected by any collateral and disturbing influences, but were manifested in precisely the same manner by different persons. It takes no account of the defects and hinderances which obstruct the normal action of the understanding. Modified Logic, on the other hand, considers Thought as it is, and not merely as it ought to be. It regards "the Causes of Error and the Impediments to Truth by which man is beset in the employment of his Faculties, and what are the means of their removal." And yet it is a universal science, much so as Pure Logic; for it does not consider the Matter of Thought. The obstacles and imperfections which it points out are not those which arise from the objects of inquiry, but from the inquiring mind. They are subjective or psychological causes of error. Lord Bacon is probably the first philosopher who attempted a systematic enumeration of the causes of error. He made a quaint classification of them, under the significant name of Idols, into the four genera of Idols of the Tribe, or the necessary faults and imperfections of the human intellect itself; Idols of the Den, which arise from the special constitution, education, and habits of each individual man; Idols of the Forum, proceeding from the defects of the language which we are obliged to employ as an instrument of Thought and a means

of communication; and Idols of the Theatre, or the various dogmas of ill-founded systems of philosophy which have found their way into men's minds through tradition, negligence, and credulity.

But Modified Logic is not properly called Logic, as it is a branch of Psychology, which treats of the phenomena of mind in general, and not merely of the normal action and necessary laws of one special faculty, the Understanding. As Modified Logic, however, is nearly allied in purpose with the Doctrine of Method, both looking to the same general end, the attainment of truth through the proper regulation of the Thinking Faculty, the two may well be considered together, under the general name of Applied Logic, as a kind of supplement to the science properly so called. Moreover, the connection between Thought and Language being so intimate, as we have seen, that neither can exist without the other, it would be an injurious, and, in fact, an impossible refinement, in a Treatise on Logic, to try to avoid frequent reference to those mistakes in thinking which proceed from an incautious use of words.

The utility of the study of Logic at least, of Formal Logic has been, perhaps, more generally doubted or denied, during the last two or three centuries, than that of any other recognized science. In England especially, ever since Bacon's time, but more particularly since that of John Locke, the study has been as unreasonably decried as it was, during an earlier period, unduly exalted. The popular voice has been against it, and, till within the last thirty years, it steadily lost ground even in the Universities, where the popular voice is not often heard or respected. This unjust depreciation of the study was due in great part to the extravagant pretensions formerly put forward in its favor. An age which acknowledged Bacon and Descartes to be its intellectual leaders was likely to scrutinize with extreme jealousy the claims of a science long held forth by

its votaries as the science or art "of the right use of reason," or "of forming instruments for the direction of the mind"; as "the head and culminating point of philosophy," "the art of thinking," "the medicine of the mind," "the lighthouse of the intellect," "ars artium et scientia scientiarum, qua aperta, omnes alice aperiuntur, et qua clausa, omnes aliæ clauduntur." Especially was this the case, as a dark shade had already been cast upon this boastful study by the rapid decline and visibly approaching extinction of those systems of philosophy, theology, and physical science which acknowledged the same parentage, and had long been associated with it in asserted pre-eminence and exclusiveness.

Logic fared not much better in the hands of those, its later disciples, who abated the extravagance of its pretensions, indeed, and, by throwing aside many of its technicalities and nice distinctions, rendered its aspect less abstruse and forbidding. But, still adhering to the opinion that its main purpose was to furnish practical rules for the guidance of the understanding in the search after truth, they destroyed its unity, broke down the boundaries which separate it from Psychology, Grammar, and Metaphysics, and encumbered it with a mass of disciplinary precepts which would be out of place anywhere but in treatises on practical education. The authors of the excellent "Art of Thinking," which commonly passes under the name of the "PortRoyal Logic," deemed it necessary to apologize even for the limited space which they had devoted to the special doctrines of this science, on the ground that "custom has introduced a sort of necessity of having at least a slight knowledge of Logic"; and they remarked, that, as the heads of chapters sufficiently indicated the topics considered in them, those of exclusively logical import might be omitted in the perusal without serious injury to what remained. "When we thought any matter might be of service in

forming the judgment," they added, "we never scrupled to insert it, to whatever science it might belong"; and, accordingly, "in this Treatise, the reader will find many things relating to Physics and Ethics, [still more, they should have added, belonging to Grammar,] and almost as much Metaphysics as it is necessary to know." This is equivalent to denying that Logic has any claims to be considered as a distinct science, or that a thorough and systematic evolution of its principles would be of any practical benefit.

The ground of these misapprehensions is entirely removed by the view which has here been given of the province and the purpose of Logic. Its boundaries are clearly defined, its pretensions are moderate, and it accomplishes all that it is intended to perform. As a Formal Science, it takes no account of the Matter of Thought, which is all derived from processes of observation or intuition that lie beyond its province. It is not concerned with the something that is known, but only with the manner of knowing it. It is not an organon of discovery, then, or a means to be used for the extension of any science. science. It analyzes the Laws of Thought; but, as these Laws are necessary and universal,- that is, as they exist in full force even in the humblest and least-instructed intellect, it does not profess to teach anything absolutely new, but only to bring out into distinct consciousness and scientific arrangement what exists or takes place implicitly in every mind. These Laws of Thought exist there in a latent or involved form ; and we follow their guidance unconsciously, just as a person who has learned to speak and write only by moving in good society, and following the example of others, uses language in strict conformity with grammatical laws, though he is unacquainted with these laws even by name. The test of the validity of any doctrine in logical science is, that those to whom it is now for the first time communicated imme

diately recognize it as nothing new, except in the form of statement, but as a principle to which they have always conformed ever since they began to think. The purpose of Logic, then, is only to teach us how we always have thought, and not any new mode of thinking, or new precautions, through which we may avoid the errors to which we were formerly liable, or by which we may discover truths that were formerly unattainable. It has no counsels to give, except to urge careful and uniform compliance with Laws which every one admits to be authoritative and universal, and to which he has always intended to conform. As Mr. Mansel remarks, the science advises only the better performance of existing obligations, and does not attempt the imposition of new ones. "A treatise on Logic is not. designed primarily to give men facility in the practice of reasoning, any more than a treatise on Optics is intended to improve their sight; and it would be as correct for a writer on the mathematical principles of Optics to entitle his work 'Optics, or the Art of improving defective Vision,' as it is for a writer on the principles of Logic to adopt for his title, Logic, or the Art of Reasoning.'"*

Indirectly, indeed, the science may be regarded as a medicine of the mind. As it brings out into clearer consciousness the laws to which all just thinking must conform, the indistinctness and confusion of thought to which we are all liable are dissipated, and the errors which often follow the symbolic use of language, or the substitution of words for thought, are exposed and eliminated. In these respects, we think rightly as soon as we have learned to think clearly; for the necessary forms of the understanding govern without dispute, when their applicability to the case in hand has become manifest. "The progress of the sciences," says Hamilton, "consists, not merely in the accumulation of new matter, but likewise in the detection of the relations

* Introduction to Aldrich's Logic, third edition, p. lvii