Mr. Macculloch’s definition of wealth, which he considers as quite unexceptionable, is, “those articles or products which possess exchangeable value, and are either necessary, useful, or agreeable.”[28] It is not, perhaps, quite unexceptionable to use the term value in a definition of wealth. It is something like explaining _ignotum per ignotius_. But independently of this objection, the definition is so worded, that it is left in doubt whether immaterial gratifications are meant to be included in it. They are not in general designated by the terms _articles_ or _products_; and it is only made clear that it is intended to include them by a collateral remark on my definition of wealth, which I confine specifically to material objects, and by a subsequent definition of productive labour, which is made to include every gratification derived from human exertion. Mr. Macculloch, in the article on Political Economy which he published in the Supplement to the Encyclopædia Britannica, had excluded these kinds of gratification from his definition of wealth, and had given such reasons for this exclusion, as would fully have convinced me of its propriety, if I had not been convinced before. He observes that, “if political economy were to embrace a discussion of the production and distribution of all that is useful and agreeable, it would include within itself every other science; and the best Encyclopædia would really be the best treatise on political economy. Good health is useful and delightful, and therefore, on this hypothesis, the science of wealth ought to comprehend the science of medicine: civil and religious liberty are highly useful, and therefore the science of wealth must comprehend the science of politics: good acting is agreeable, and therefore, to be complete, the science of wealth must embrace a discussion of the principles of the histrionic art, and so on. Such definitions are obviously worse than useless. They can have no effect but to generate confused and perplexed notions respecting the objects and limits of the science, and to prevent the student ever acquiring a clear and distinct idea of the inquiries in which he is engaged.”[29] On these grounds he confined wealth to material products; but, in the same treatise, he included, in his definition of productive labour, all those sources of gratification which he had, with such good reason, excluded from his definition of wealth. When he had done this, however, he could not but be struck with the inconsistency of saying that wealth consisted exclusively of material products, and yet that all labour was equally productive of wealth, whether it produced material products or not. To get rid of this inconsistency, he has now altered his definition, by leaving out the term material products; and it remains to be seen, whether in so doing he has not essentially deviated from the most obvious rules which should direct us in defining our terms.