That if each spadefull of earth were lifted but an inch or two above the barrow beyond what was necessary, a still greater waste of force would arise. That if the barrow itself had its wheel at a distance beyond the centre of its load, it would be more fatiguing to draw. That if the barrow had upright sides, it would require more exertion to turn out its load than if its sides were much inclined. Thus although Q. might have less strength and less activity than P., he might yet by skill and practice, have arrived at some combination of these tools which should enable him with less fatigue to do more daily work than P. But in order to have arrived at this degree of skill, Q. must when a boy have been taught to examine _separately_ the consequences of any defect or inconvenience in the parts of the tools he was to use in after life, or in the modes of using them. If not so taught, he must have arrived at the same knowledge by the slower and more painful effort of his own reflections. In either case he would be able to communicate his knowledge to his friends or his children; and if circumstances induced or obliged him to enter upon a new trade, he would naturally apply those principles to his new tools. Indeed, whatever subject might be presented to a mind thus trained, such habits of inquiry would most probably be applied to its examination. Thus, by the early education of his reasoning faculties on the trade by which he is to subsist, he would not only render his own labour more productive, but would have his mind better prepared for the reception of other truths. CHAPTER II. ERROR RESPECTING THE INTERCHANGE OF COMMODITIES. There exists in society a widely-spread error relating to the very principle of that interchange of property between individuals which is usually called a bargain. It is almost always supposed that one party is a gainer whilst the other is a loser. Indeed, by those whose reasoning on the subject has been limited to this single view of the question, it is with some plausibility maintained, that since the quantity of the commodities interchanged is in no case augmented by the bargain, the gain of one party can be accomplished only by an equal loss on the part of the other. The insufficiency of this reasoning depends upon the truth of the principle that each party, being the best judge of the pleasure or advantage he can derive from the possession of a thing, _himself_ decides that in his own case it will be increased by the exchange.