with respect to the successive impressions which are made on the same parts of the body, and consequently according to the material hypothesis, on the same parts of the thinking substance; and that it may be deduced generally from the nature of thought itself, and the associations which arise from similarity, &c., that this principle must be entirely nugatory with respect to the associations of the ideas of different senses, even though it should hold true with respect to those of any one sense; lastly, that all ideas impressed at the same time acquire a power of exciting one another afterwards without any regard to the coincidence of their imaginary seats in the brain, and that therefore the true account of the principle of association must be derived from the first cause, the coincidence of time, and not from the latter cause, the proximity of situation, which bears no manner of proportion to the effects produced.
I have always had the same feeling with respect to Hartley (still granting his power to the utmost) which is pleasantly expressed in an old author, Roger Bacon, quoted by Sir Kenelm Digby in his answer to Sir Thomas Browne. “Those students,” he says, “who busy themselves much with such notions as relate wholly to the fantasie, do hardly ever become idoneous for abstracted metaphysical speculations; the one having bulky foundation of matter or of the accidents of it to settle upon (at the least with one foot): the other flying continually, even to a lessening pitch, in the subtil air. And accordingly, it hath been generally noted, that the exactest mathematicians, who converse altogether with lines, figures, and other differences of quantity, have seldom proved eminent in metaphysicks or speculative divinity. Nor again, the professors of these sciences in the other arts. Much less can it be expected, that an excellent physician, whose fancy is always fraught with the material drugs that he prescribeth
