8 



INTRODUCTION. 



the operations have in any individual 

 case been rightly or wrongly per- 

 formed : in the same manner as the 

 science of music teaches us to dis- 

 criminate between musical notes, and 

 to know the combinations of which 

 they are susceptible, but not what 

 number of vibrations in a second cor- 

 respond to each ; which, though use- 

 ful to be known, is useful for totally 

 different purposes. The extension of 

 Logic as a Science is determined by 

 its necessities as an Art : whatever it 

 does not need for its practical ends, 

 it leaves to the larger science which 

 may be said to correspond, not to 

 any particular art, but to art in gene- 

 ral ; the science which deals with the 

 constitution of the human faculties ; 

 and to which, in the part of our men- 

 tal nature which concerns Logic, as 

 well as in all other parts, it belongs 

 to decide what are ultimate facts, and 

 what are resolvable into other facts. 

 And I believe it will be found that 

 most of the conclusions arrived at in 

 "ihis work have no necessary connexion 

 with any particular views respecting 

 the ulterior analysis. Logic is com- 

 mon ground on which the partisans of 

 Hartley and of Reid, of Locke and of 

 Kant may meet and join hands. 

 Particular and detached opinions of 

 all these thinkers will no doubt occa- 

 sionally be controverted, since all of 

 them were logicians as well as meta- 

 physicians ; but the field on which 

 their principal battles have been 

 fought, lies beyond the boundaries of 

 our science. 



It cannot, indeed, be pretended 

 that logical principles can be alto- 

 gether irrelevant to those more ab- 

 struse discussions ; nor is it possible 

 but that the view we are led to take 

 of the problem which logic proposes, 

 must have a tendency favourable to 

 the adoption of some one opinion, on 

 these controverted subjects, rather 

 than another. For metaphysics, in 

 endeavouring to solve its own peculiar 

 problem, must employ means, the 

 validity of which falls under the 

 cognizamce of logic. It proceeds, no 



doubt, as far as possible, merely by 

 a closer and more attentive interroga- 

 tion of our consciousness, or more 

 properly speaking, of our memory ; 

 and so far is not amenable to logic. 

 But wherever this method is insuffi- 

 cient to attain the end of its inqiiiries, 

 it must proceed, like other sciences, 

 by means of evidence. Now, the 

 moment this science begins to draw 

 inferences from evidence, logic be- 

 comes the sovereign judge whether 

 its inferences are well grounded, or 

 what other inferences would be so. 



This, however, constitutes no nearer 

 or other relation between logic and 

 metaphysics, than that which exists 

 between logic and every other science. 

 And I can conscientiously affirm, that 

 no one proposition laid down in this 

 work has been adopted for the sake 

 of establishing, or with any reference 

 to its fitness for being employed in 

 establishing, preconceived opinions in 

 any department of knowledge or of 

 inquiry on which the speculative 

 world is still undecided.* 



* The view taken in the text, of the defi- 

 nition and purpose of Logic, stands ia 

 marked opposition to that of the scliool of 

 philosophy wliich, in this country, is re- 

 presented by the writings of Sir William 

 Hamilton and of his numerous pupils. 

 Logic, as this school conceives it, is " the 

 Science of the Formal Laws of Thought ;" 

 a definition framed for the express purpose 

 of excluding, as irrelevant to Logic, what- 

 ever relates to Belief and Disbelief, or to 

 the pursuit of truth as such, and restrict- 

 ing the science to that very limited portion 

 of its total province, which has reference 

 to the conditions, not of Truth, but of 

 Consistency. What I have thought it use- 

 ful to say in opposition to this limitation 

 of the field of Logic, has been said at some 

 length in a separate worl<, first published 

 in 1865, and entitled An Examination of 

 Sir William Hamilton's Philosophy, and of 

 the Principal Philosophical Questions dis- 

 cussed in his Writings. For the purposes of 

 the present Treatise, I am content that the 

 justification of the larger extension which 

 I gave to the domain of the science, should 

 rest on the sequel of the Treatise itself. 

 Some remarks on the relation which the 

 Logic of Consistency bears to the Logic of 

 Truth, and on the place wliich that par- 

 ticular part occupies in the whole to which 

 it belongs, will be found in the present 

 volume (J3ook II, chap. iii. § 9). 



