14 



Though Mr Mansel does not acknowledge any subjec- 

 tive conditions of intuition besides Space and Time, he does 

 recognize other kinds of necessity, which, I should equally refer 

 to Fundamental Ideas ; because they are, no less than Space 

 and Time, the foundations of universal and necessary truths 

 in science. Such are (Prol. Log. p. 123) the Principle of 

 Substance ; All Qualities exist in some subject : and the 

 Principle of Causality; Every Event has its Cause. To 

 these Principles he ascribes a " metaphysical necessity," the 

 nature and grounds of which he analyses with great acuteness. 

 But what I have to observe is, that whatever differences may 

 be pointed out between the grounds of the necessity, in this 

 case of metaphysical necessity, and in that which Mr M. 

 calls mathematical necessity which belongs to the Conditions 

 or Ideas of Space and of Time ; still, it is not the less true 

 that the Ideas of Substance and of Cause, do afford a foun- 

 dation for necessary truths, and that on these truths are 

 built Sciences. That every Change must have a Cause, with 

 the corresponding Axioms, that the Cause is known by the 

 Effect, and Measured by it, is the basis of the Science of 

 Mechanics. That there is a Substance to which qualities, 

 belong, with the corresponding Axiom, that we cannot 

 create or destroy Substance, though we may alter Qualities 

 by combining and separating Substances, is the basis of 

 the Science of Chemistry. And that this doctrine of the 

 Indestructibility of Substance is a primary axiomatic truth, 

 is certain; both because it has been universally taken for 

 granted by men seeking for general truths ; and because it 

 is not and cannot be proved by experience. (See Phil. Ind. 

 Sc. B. vi. chap. 3). So that I have here, even according to 

 Mr Mansel's own statement, other grounds besides Space 

 and Time, for necessary truths in Science. 



Besides mathematical and metaphysical necessity, Mr 

 Mansel recognizes also a logical necessity. I will not pretend 





