UNDERSTANDING, or JUDGMENT, in the Hartleyan acceptation of the term, is that faculty by which we contemplate mere sensations and ideas, pursue truth, and assent to, or dissent from, proposi tions. In this article, and in WORDS, we 'shall, as we proposed in Pnnosoray, mental, § 104, lay before our readers a view of the highly important principles of Hartley respecting the understanding, occasionally making in his statements such alterations as will best adapt them to our object.
Whatever be the precise nature of as sent and dissent, they must class with ideas, being only those very complex in ternal feelings which are connected by as sociation with those groups of words, which are called propositions in general, or affirmations and negations in partici), lar.—Assent (and consequently its oppo site, dissent) may be distinguished into two kinds, rational and practical. Ration al assent to any proposition may be de fined a readiness to affirm it to be true, proceeding from a close association of the ideas suggested by the proposition, with the idea or internal feeling belonging to the word truth; or of the terms of the proposition with the word truth. Ra, tional dissent is the opposite to this.—, Practical assent is a readiness to act in such a manner as the frequent vivid re currency of the rational assent disposes us to act ; and practical dissent the trary.
Practical assent is then the natural con sequence of rational assent, when suffici tntly impressed. It must, however, be observed, first, that some propositions, mathematical ones for instance, admit on ly of a rational assent, the practical not • being applied to them in common cases : secondly, that the practical assent is some. times generated, and arrives at a high de gree of strength, without any previons rational assent, and by methods Which have little or no connection with it ; yet still is in general much influenced by it,i and, conversely, exerts a great influence P;1 upon it : thirdly, practical assent may be IV in opposition to rational assent, and in.( consequence of its having been long and firmly cultivated, may altogether pre vent the latter from influencing the eon-' duct.
Let us next inquire into the causes o rational and practical assent, beginning, 1. with that given to mathematical con.
clusions.—Now the original cause that a person affirms the truth of the propoi'i, ton, twice two are foi;r, is the entire co incidence of the visible or tangible idea of twice two, with that of four, as impress ed upon• the mind by various objects. We see every where that both are only different names for the same impression ; and it can only be in consequence of as sociation, that the word truth, its defini tion, or internal feeling, becomes appro -priated to this coincidence.—Where the numbers are so large that we cannot form any distinct visible ideas of them, as when we say 12 times 12 are equal to 144, rational assent is founded (if not on the authority of a table or a teacher) on a co incidence of words arising from some method of reckoning up 12 times 12, so as to conclude with 144, and resembling the coincidence of words which attends the before-mentioned coincidence of ideas in the simpler numerical proposi tions.—The operations of addition, sub traction, multiplication, division, and ex traction of roots, with all the most com-, plei operations relating to algebraic quantities, considered as the denotements of numbers, are no more than methods of producing this coincidence of words, thunded upon and rising above one ano ther. And it is merely association again which appropriates the word truth, &c. to the coincidence of the words or sym bols which denote the numbers.
This coincidence of terms is considered as a proof that the visible ideas of the numbers under consideration would coin cide as much as the visible ideas of twice two and four, were the former equally distinct with the latter; and indeed the same thing may be fully proved, and of ten is so, by experiments with counters, lines, &c. And hence, thinking persons, who make a distinction often unthought of, between the coincidence of terms and that of ideas, consider the real and abso lute truth to be as great in complex nu merical propositions, as in the simplest. Now as it is impossible to gain distinct vi sible ideas of different numbers, where at least they are_considerable, terms de noting them are a necessary means ofdis tingishing them one from another, so as reason justly respecting them.