ideas of these, and their mutual connexion by means of association taken together and operating on one another” (i. 80). And in harmony with this (i. 101), he afterwards gives a formal derivation of ideal vibratiuncles from sensory vibrations; and (103) talks of that “idea or state of mind, _i.e._ set of compound vibratiuncles, which we term the WILL;” and again (p. 212) he says, “the permanence of sensations is of the nature of an idea.” Here the great {286} mystery which puzzled the Greeks so much, the mysterious bond which unites the ἕν and the πολλά--the one and the many--is solved very decidedly, as it would appear, on the Epicurean side. It is not the one which produces the many, but the many which produce the one; the one--what I call Mind, Will--is only a modification of the many. The radical objection to all this is that every man who is not a professional metaphysician feels it to be nonsense; the popular feeling protests; Shakespeare, who represents the thoughts and the language of a high and a healthy humanity, never talks in this style; and, more than that, the profoundest thinkers from Plato down to Hegel find in the proposition that thought is manufactured out of sensations a much greater mystery than that which this theory was invented to explain. One feels conscious that sensations might go on for ever, and not produce anything that had the slightest semblance to a thought; just as rain and sunshine acting on thistle-down from summer to summer produce only thistles and not roses. It appears, indeed, that our inductive philosopher is here involving himself in the vulgar fallacy of confounding the occasion or the condition of a thing with the cause. An accidental occasion, or an indispensable condition, are equally remote from the idea of a cause. The accidental occasion, for instance, of a house being built on a certain site, is that a certain gentleman, happening to take a walk in a certain district, and being not averse to house-building, determines to have a house on that site; the indispensable condition of the house being erected is that there should be a site for it to stand on, and stone and lime for it to be built with; but the only proper efficient {287} cause of the house being a house is the mind of the architect, the plan which that mind originates, and the instructions which he gives to the contractor, and the contractor to the masons. The sensuous tendency which Hartley’s medical studies had given to his thoughts comes out strongly in another passage (i. 342), where he attempts to explain the evidence of mathematical axioms:--“We infer that 2+2=4 only from prior instances of having actually perceived this; and from the necessary coincidence of all these instances with all other possible ones.” This recalls a famous passage in J. Stuart Mill’s treatise against Sir W. Hamilton, in which he stamps with his authority the ingenious demonstration of a London barrister, to the effect that “in some possible world two and