FALLACIES OF SIMPLE INSPECTION. 315 



to give objectivity to a law of the mind to suppose that 

 what is true of our ideas of things must be true of the things 

 themselves exhibits itself in many of the most accredited 

 modes of philosophical investigation, both on physical and on 

 metaphysical subjects. In one of its most undisguised mani- 

 festations, it embodies itself in two maxims, which lay claim 

 to axiomatic truth : Things which we cannot think of together, 

 cannot coexist ; and Things which we cannot help thinking of 

 together, must coexist. I am not sure that the maxims were 

 ever expressed in these precise words, but the history both of 

 philosophy and of popular opinions abounds with exemplifica- 

 tions of both forms of the doctrine. 



To begin with the latter of them : Things which we 

 cannot think of except together, must exist together. This 

 is assumed in the generally received and accredited mode of 

 reasoning which concludes that A must accompany B in 

 point of fact, because "it is involved in the idea." Such 

 thinkers do not reflect that the idea, being a result of abstrac- 

 tion, ought to conform to the facts, and cannot make the facts 

 conform to it. The argument is at most admissible as an 

 appeal to authority ; a surmise, that what is now part of the 

 idea, must, before it became so, have been found by previous 

 inquirers in the facts. Nevertheless, the philosopher who 

 more than all others made professions of rejecting authority, 

 Descartes, constructed his system on this very basis. His 

 favourite device for arriving at truth, even in regard to 

 outward things, was by looking into his own mind for it. 

 " Credidi me," says his celebrated maxim, " pro regula 

 generali sumere posse, omne id quod valde dilucide et 

 distincte concipiebam, verum esse;" whatever can be very 

 clearly conceived, must certainly exist ; that is, as he after- 

 wards explains it, if the idea includes existence. And on this 

 ground he infers that geometrical figures really exist, because 

 they can be distinctly conceived. Whenever existence is 

 " involved in an idea," a thing conformable to the idea must 

 really exist ; which is as much as to say, whatever the idea 

 contains must have its equivalent in the thing ; and what we 



