Thus far in our study, we have assumed that we knew what competition was. Now, however, as we are to study it scientifically, we are in need of an exact definition, that we may know just what the term includes. Prof. Sturtevant, in his "Economics," says: "_Competition is that law of human nature by which every man who makes an exchange will seek to obtain as much as he can of the wealth of another for a given amount of his own wealth._" Simmer this down to its essence, and we have simply: _Competition is selfishness._ To the other evident faults of the definition we need not allude. It is a much more satisfactory definition which Webster's Dictionary gives us, for it includes the idea that competition necessitates two or more parties to exercise it: "_Competition is the act of seeking the same object that another is seeking._" But this is too broad a definition for our purpose. It takes in competitions for fame, social standing, etc., with which we have nothing to do. Failing to find a satisfactory definition, let us make one, as follows: _Competition is that force of rivalry between buyers or between sellers which tends to make the former give a greater price for the commodity they wish to secure, and tends to make the latter offer better commodities for a less price._ That competition _is_ a force, even in the popular estimation, is evidenced by such common expressions as "the pressure of competition," "a strong competition," and indeed, "the force of competition." But these very expressions show us as well, what we have already found to be true in the preceding chapters, that it is not a constant force but a variable one. What, then, are the laws of its variation?