^42 



INDUCTION. 



mind on body to be a demonstrated im- 

 possibility.* 



A doctrine more precisely the reverse 

 of the Volitional theory of causation can- 

 not well be imagined. The Volitional 

 theory is, that we know Ijy intuition or 

 by direct experience the action of our own 

 mental volitions on matter ; that we may 

 hence infer all other action upon matter 

 to be that of volition, and might thus 

 know, without any other evidence, that 

 matter is under the governmentof a divine 

 mind. Leibnitz and the Cartesians, on the 

 contrary, maintain that our volitions do 

 not and cannot act upon matter, and that 

 it is only the existence of an all-governing 

 Being, and that Being omnipotent, which 

 can account for the sequence between our 

 volitions and our bodily actions. When 

 we consider that each of these two theories, 

 which, as theories of causation, stand at 

 the opposite exti-emes of possible diver- 

 gence from one another, invokes not only 

 as its evidence, but as its sole evidence, 

 the absolute inconceivability of any theory 

 but itself, we are enabled to measure the 

 worth of this kind of evidence ; and when 

 we find the Volitional theory entirely built 

 upon the assertion that by our mental 

 constitution we are compelled to recognise 

 our volitions as eflficient causes, and then 

 find other thinkers maintaining that we 

 know that they are not and cannot be 

 such causes, and cannot conceive them to 

 be so, I think we have a right to say that 

 this supposed law of our mental constitu- 

 tion does not exist. 



Dr.Tulloch (pp. 45-47)thinksita sufficient 

 answer to this that Leibnitz and the Car- 

 tesians were Tbeists, and believed the will 

 of God to be an efficient cause. Doubtless 

 they did, and the Cartesians even believed 

 (though Leibnitz did not) that it is the only 

 surh cause. Dr. TuUoch mistakes the na- 

 ture of the question. I was not writing 

 on Theism, as Dr. Tulloch is, biit against a 

 particular theory of causation, which, if it 

 be unfounded, can give no effective support 

 to Theism or to anything else. I found it 

 asserted that volition is the only efficient 

 cause, on the ground that no other efficient 

 cause is conceivable. To this assertion I 

 oppose the instances of Leibnitz and of the 

 Cartesians, who affirmed with equal posi- 

 tiveness that volition as an efficient cause 

 is itself not conceivable, and that omnipo- 



* In the words of Fontenelle, another 

 celebrated Cartesian, " Les philosophes 

 aussi bien que le peuple avaient cru que 

 Time et le corps agissaient r^ellement et 

 physiquement i'un sur I'autre. Descartes 

 Vint, qui prouva que leur nature ne per- 

 mettait point cette sorte de communication 

 veritable, et qu'ils n'en pouvaient avoir 

 qu'uiie apparente, dont Dieu ^taitle M6dia- 

 teur." — (Envreade Fontenelle, ed. 1767, torn, 

 v. p. 534. 



tence, which renders all things conceivable, 

 can alone take away the impossibility. 

 This I thought, and think, a conclusive 

 answer to the argument on which this 

 theory of causation avowedly depends. 

 But I certainly did not imagine that Theism 

 w;i8 bound up with that theory ; nor ex- 

 pected to be charged with denying Leibnitz 

 and the Cartesians to be Theists because I 

 denied that they held the ttieory 



CHAPTER VI. 



ON THE COMPOSITION OF CAUSES. 



§ I. To complete the general notion 

 of causation on which the rules of ex- 

 perimental inquiry into the laws of 

 nature must be founded, one distinc- 

 tion still remains to be pointed out : 

 a distinction so radical, and of so 

 much importance, as to require a 

 chapter to itself. 



The preceding discussions have ren- 

 dered us familiar with the case in 

 which several agents, or causes, con- 

 cur as conditions to the production of 

 an effect ; a case, in truth, almost uni- 

 versal, there being very few effects to 

 the production of which no more than 

 one agent contributes. Suppose, then, 

 that two different agents, operating 

 jointly, are followed, under a certain 

 set of collateral conditions, by a given 

 effect. If either of these agents, in- 

 stead of being joined with the other, 

 had operated alone, under the same 

 set of conditions in all other respects, 

 some effect would probably have fol- 

 lowed ; which would have been diffe- 

 rent from the joint effect of the two, 

 and more or less dissimilar to it. Now, 

 if we happen to know what would be 

 the effect of each cause when acting 

 separately from the other, we are often 

 able to arrive deductively, or d priori, 

 at a correct prediction of what will 

 arise from their conjunct agency. To 

 render this possible, it is only neces- 

 sary that the same law which expresses 

 the effect of each cause acting by it- 

 self shall also correctly express the 

 part due to that cause of the effect 

 which followt from the two together. 



