In the second place, the assumption made tacitly, at least, if not avowedly, that political economy is an exact science is wholly misleading. Political economy covers a wide range of subjects of which the tariff is only one; but in none of its branches is it an exact science. Modern investigation has, no doubt, revealed certain economic laws which we may fairly say operate with reasonable certainty, but this is a very different proposition from that which would make the conclusions of economists in all directions as absolute as those of mathematicians. Political economy, in fact, does not differ greatly in this respect from history, because both deal with subjects where the conditions and sympathies of men and women play a large part, and where human passions are deeply engaged. In fields like these, where the personal equation of humanity plays a controlling part, it is absurd to attempt to argue as if we were dealing with a mathematical formula. There may be a philosophy of political economy as there is of history; there may be scientific methods of dealing with it and certain economic laws, subject to many exceptions, which we may consider to be established, but nevertheless it is as far from being an exact science as one can conceive. The exact science notion is the misconception of cloistered learning which can build impregnable systems where there are none to attack them, but which has no idea of the practical difficulties of an unsympathetic world where the precious system must meet every possible objection and not merely those devised by its framers. In discussing a question of political economy, therefore, it is well to bear in mind that we are handling a subject where new facts are always entering in to modify old conclusions, and where there are many conditions, the effect of which it is impossible to calculate.