To confine ourselves to production: If the laws of the production of all objects, or even of all material objects, which are useful or agreeable to mankind, were comprised in Political Economy, it would be difficult to say where the science would end: at the least, all or nearly all physical knowledge would be included in it. Corn and cattle are material objects, in a high degree useful to mankind. The laws of the production of the one include the principles of agriculture; the production of the other is the subject of the art of cattle-breeding, which, in so far as really an art, must be built upon the science of physiology. The laws of the production of manufactured articles involve the whole of chemistry and the whole of mechanics. The laws of the production of the wealth which is extracted from the bowels of the earth, cannot be set forth without taking in a large part of geology. When a definition so manifestly surpasses in extent what it professes to define, we must suppose that it is not meant to be interpreted literally, though the limitations with which it is to be understood are not stated. Perhaps it will be said, that Political Economy is conversant with such only of the laws of the production of wealth as are applicable to _all_ kinds of wealth: those which relate to the details of particular trades or employments forming the subject of other and totally distinct sciences. If, however, there were no more in the distinction between Political Economy and physical science than this, the distinction, we may venture to affirm, would never have been made. No similar division exists in any other department of knowledge. We do not break up zoology or mineralogy into two parts; one treating of the properties common to all animals, or to all minerals; another conversant with the properties peculiar to each particular species of animals or minerals. The reason is obvious; there is no distinction _in kind_ between the general laws of animal or of mineral nature and the peculiar properties of particular species. There is as close an analogy between the general laws and the particular ones, as there is between one of the general laws and another: most commonly, indeed, the particular laws are but the complex result of a plurality of general laws modifying each other. A separation, therefore, between the general laws and the particular ones, merely because the former are general and the latter particular, would run counter both to the strongest motives of convenience and to the natural tendencies of the mind. If the case is different with the laws of the production of wealth, it must be because, in this case, the general laws differ in kind from the particular ones. But if so, the difference in kind is the radical distinction, and we should find out what that is, and found our definition upon it.