It is perhaps impossible, in a few words, to describe precisely the nature of the operation termed reasoning. In general terms it may be defined, _the means we employ for the attainment of the end proposed; the employment of knowledge for the discovery of truth_; or _the process of demonstration_; whether the object be an arithmetical sum, a geometrical problem, or a discourse on taste. A part of the process of reasoning, according to received opinion, consists in comparison, either of things, or of general terms; and this comparison implies not merely their exterior similitude, but likewise their internal structure and composition: because two mineral substances may resemble each other in external appearance, and may wholly differ in their intrinsic properties. The process of ascertaining wherein they agree, and the circumstances which discriminate them, is an instance of reasoning, or the means we employ for the proposed end, and which means necessarily imply the previous possession of knowledge. It will also be seen that in the instance adduced, and indeed in most others, where we reason on things, that precision can only be attained through the medium of number; for these mineral substances, although similar in external character, may contain very different proportions of the precious metals, and their actual value can only be estimated by comparison; that is, by an analysis, founded in knowledge, to ascertain the per centage of gold or silver, which must be expressed in numbers: and the comparison that is instituted concerning general or abstract terms, must have for its basis the establishment of their legitimate force and meaning. When we consult authorities on this subject, and particularly Dr. Johnson's dictionary, we find that he has given eleven different significations of the term _reason_, which he defines to be "the power by which man _deduces_ one proposition from another, or proceeds from premises to consequences." There is, however, much ambiguity in this statement; and it would perhaps be impossible, in reasoning concerning things, (which is to be considered as the most perfect example of this process,) to adduce an instance, in which one proposition is strictly _deduced_ from another.