So far as possible up to this point we have attempted to avoid controverted questions, and to expound those principles and laws of monetary science which are regarded as true by the most competent persons. It is now desirable, however, that we should discuss a topic regarding which opinions differ widely. For more than a quarter of a century bimetallism has been a cause of contention in academic and business circles and in legislative halls, and, though practice tends more and more in the direction of gold monometallism, scholars, business men, and statesmen are not yet in agreement regarding it. In the present chapter we shall confine our attention to the theory of the subject, leaving its more practical aspects for subsequent treatment. It is first of all necessary to understand the meaning of the term and the purpose of the advocates of this particular doctrine.