Perfect Competition, Historically Contemplated

No concept in economics — or elsewhere — is ever defined fully, in the sense that its meaning under every conceivable circumstance is clear. Even a word with a wholly arbitrary meaning in economics, like ‘elasticity’, raises questions which the person who defined it (in this case, Marshall) never faced: for example, how does the concept apply to finite changes or to discontinuous or stochastic or multiple-valued functions ? And of course a word like ‘competition’, which is shared with the whole population, is even less likely to be loaded with restrictions or elaborations to forestall unfelt ambiguities.