dation of human thoughts and actions than I have hitherto done. At present I have laid aside all thoughts of this kind as I have neither time nor strength for such an undertaking; and the most that I shall attempt is to point out such contradictions and difficulties in both these systems as may lessen the weight of any objections drawn from them against the one I have stated, and leave the argument as above explained in its original force.
To begin with the doctrine of association. The general principle of association as laid down by Hartley is this; that if any given sensation, idea, or motion, be for a number of times either accompanied, or immediately followed by any other sensation, idea, or muscular motion, the recurrence of the one will afterwards mechanically give rise to that of the other. By immediately followed I mean closely followed; for suppose A to be associated with B, and B with C, A will not only produce B and C intermediately, but will in time produce C immediately without the inter- vention of B. A mathematician would perhaps here ask how this can ever be actually proved: for though it seems reasonable to suppose that the influence of A if it extend to B should also go a little farther to the next idea, and join indirectly and secretly with B in producing C, yet as the connection between A and B must be stronger than that between A and C, if in any case the connection between the former become gradually so weakened as to dissolve of itself, the latter must fail of course, and therefore C can never follow A, except when B stands equivocally between them. This question would go upon the supposition, that B and C must always be impressions of exactly the same kind and degree of strength, which is not the case. A, though more remote from C, may yet be more intimately connected with it than with B from several other causes,
