ON THE DEFINITION OF POLITICAL ECONOMY; AND ON THE METHOD OF INVESTIGATION PROPER TO IT. It might be imagined, on a superficial view of the nature and objects of definition, that the definition of a science would occupy the same place in the chronological which it commonly does in the didactic order. As a treatise on any science usually commences with an attempt to express, in a brief formula, what the science is, and wherein it differs from other sciences, so, it might be supposed, did the framing of such a formula naturally precede the successful cultivation of the science. This, however, is far from having been the case. The definition of a science has almost invariably not preceded, but followed, the creation of the science itself. Like the wall of a city, it has usually been erected, not to be a receptacle for such edifices as might afterwards spring up, but to circumscribe an aggregation already in existence. Mankind did not measure out the ground for intellectual cultivation before they began to plant it; they did not divide the field of human investigation into regular compartments first, and then begin to collect truths for the purpose of being therein deposited; they proceeded in a less systematic manner. As discoveries were gathered in, either one by one, or in groups resulting from the continued prosecution of some uniform course of inquiry, the truths which were successively brought into store cohered and became agglomerated according to their individual affinities. Without any intentional classification, the facts classed themselves. They became associated in the mind, according to their general and obvious resemblances; and the aggregates thus formed, having to be frequently spoken of as aggregates, came to be denoted by a common name. Any body of truths which had thus acquired a collective denomination, was called a _science_. It was long before this fortuitous classification was felt not to be sufficiently precise. It was in a more advanced stage of the progress of knowledge that mankind became sensible of the advantage of ascertaining whether the facts which they had thus grouped together were distinguished from all other facts by any common properties, and what these were. The first attempts to answer this question were commonly very unskilful, and the consequent definitions extremely imperfect.