Now the Sophist and the popular moralist, in that preliminary attempt to define the nature of Justice--what is right, are both alike trying, first in this formula, then in that, to occupy, by a thought, and by a definition which may convey that thought into the mind of another--to occupy, or cover, a certain area of the phenomena of experience, as the Just. And what happens thereupon is this, that by means of a certain kind of casuistry, by the allegation of certain possible cases of conduct, the whole of that supposed area of the Just is occupied by definitions of Injustice, from this centre or that. Justice therefore- -its area, the space of experience which it covers, dissolves away, literally, as the eye is fixed upon it, like Heraclitean water: it is and is not. And if this, and the like of this, is to the last all that can be known or said of it, Justice will be no current coin, at least to the acute philosophic mind. But has some larger philosophy perhaps something more to say of it? and the power of defining an area, upon which no definition of Injustice, in any conceivable case of act or feeling, can infringe? That is the question upon which the essential argument of The Republic starts--upon a voyage of discovery. It is Plato's own figure. There, clearly enough, may be seen what the difference, the difference of aim, between Socrates [115] and the Sophists really was, amid much that they had in common, as being both alike distinguished from that older world of opinion of which Simonides is the mouthpiece.