The lectures, published posthumously, became a text-book for students, and reached a nineteenth edition in 1851. Their faults, considered as philosophical treatises, are palpable. They have the wordiness of hasty composition, and the discursive rhetoric intended to catch the attention of an indolent audience. Brown does not see that he is insulting his hearers when he apologises for introducing logic into lectures upon metaphysics, and indemnifies them by quotations from Akenside and the _Essay on Man_. Brown, however, showed great acuteness and originality. He made deviations, and took pains to mark his deviations, from Reid, though he spoke more guardedly of his own friend, Stewart. Stewart, who had strongly supported Brown's election, was shocked when, on the publication of the lectures, he came to discover that his colleague had been preaching heresy, and wrote with obvious annoyance of Brown's hastiness and dangerous concessions to the enemy.[468] Brown, however, impressed his contemporaries by his ability. Sydney Smith is probably reporting the current judgment of his own circle when he says[469] that in metaphysics Stewart was a 'humbug' compared with Brown. I certainly think that Stewart, whom I should be sorry to call a humbug, shows less vigour and subtlety. Brown, at any rate, impressed both the Mills, and his relation to them is significant. Brown's essay upon Causation indicates this relation. In this, indeed, there is little, if any, divergence from Stewart, though he attacks Reid with considerable asperity. He urges that Reid, while really agreeing with Hume, affected to answer him under cover of merely verbal distinctions.[470] The main point is simple. Hume had asserted that all events seem to be 'entirely loose and separate,' or, in other words, 'conjoined but never connected.' Yet he points out that, in fact, when we have found two events to be 'conjoined,' we call one cause and the other effect, and assume a 'necessary connection' between them. He then asks, What is the origin of this belief, and what, therefore, is the logical warrant for its validity? Brown entirely accepts Hume's statement of the facts. The real meaning of our statements is evaded by appealing to the conception of 'power.' When the loadstone (in his favourite illustration) attracts the iron, we say it has a 'power' of attracting iron. But to speak thus of a power is simply to describe the same facts in other words. We assert this, and nothing more than this, that when the loadstone comes near the iron, each moves towards the other. 'Power' is a word which only covers a statement of 'invariable antecedence.' Brown traces the various confusions which have obscured the true nature of this belief. He insists especially that we can no more discover power in mental than in physical sequences. The will had been supposed to be the type of causal power; but volition, according to Brown, reveals simply another succession of desires and bodily actions.