They were true enough to give the really conclusive answer to many popular fallacies. The type of sophistry which Ricardo specially assailed was that which results from neglecting the necessary implications of certain changes. The arguments for the old 'mercantile theory'--for 'protection' of industry, for the poor-law, for resisting the introduction of machinery, the fear of 'gluts' and all manner of doctrines about the currency--were really exposed by the economists upon the right grounds. It was absurd to suppose that by simply expanding the currency, or by making industry less efficient, or forcing it to the least profitable employments, you were increasing the national wealth; or to overlook the demoralising effects of a right to support because you resolved only to see the immediate benefits of charity to individuals. It is true, no doubt, that in some cases there might be other arguments, and that the economists were apt to take a narrow view of the facts. Yet they decisively exploded many bad arguments, and by the right method of enforcing the necessity of tracing out the whole series of results. It was partly to their success in confuting absurd doctrines that their confidence was due; though the confidence was excessive when it was transferred to the axioms from which they professed to start. A doctrine may be true enough to expose an error, and yet not capable of yielding definite and precise conclusions. If I know that nothing can come out of nothing, I am on the way to a great scientific principle and able to confute some palpable fallacies; but I am still a very long way from understanding the principle of the 'conservation of energy.' The truth that scarcity meant dearness was apparently well known to Joseph in Egypt, and applied very skilfully for his purpose. Economists have framed a 'theory of value' which explains more precisely the way in which this is brought about. A clear statement may be valuable to psychologists; but for most purposes of political economy Joseph's knowledge is quite sufficient. It is the doctrine which is really used in practice whatever may be its ultimate justification.