Now undoubtedly the repudiation of error is not at all the same thing as embracing truth. People are often able to see the force of arguments that destroy a given opinion, without being able to see the force of arguments for the positive opinion that ought to replace it. They can only be quite sure of seeing both, when they have acquired not merely a conviction that one notion is false and another true, but have furthermore exchanged a generally erroneous way of thinking for a generally correct way. Hence the truly important object with every one who holds opinions which he deems it of the highest moment that others should accept, must obviously be to reach people's general ways of thinking; to stir their love of truth; to penetrate them with a sense of the difference in the quality of evidence; to make them willing to listen to criticism and new opinion; and perhaps above all to teach them to take ungrudging and daily trouble to clear up in their minds the exact sense of the terms they use. If this be so, a false opinion, like an erroneous motive, can hardly have even a provisional usefulness. For how can you attack an erroneous way of thinking except in detail, that is to say through the sides of this or that single wrong opinion? Each of these wrong opinions is an illustration and type, as it is a standing support and abettor, of some kind of wrong reasoning, though they are not all on the same scale nor all of them equally instructive. It is precisely by this method of gradual displacement of error step by step, that the few stages of progress which the race has yet traversed, have been actually achieved. Even if the place of the erroneous idea is not immediately taken by the corresponding true one, or by the idea which is at least one or two degrees nearer to the true one, still the removal of error in this purely negative way amounts to a positive gain. Why? For the excellent reason that it is the removal of a bad element which otherwise tends to propagate itself, or even if it fails to do that, tends at the best to make the surrounding mass of error more inveterate. All error is what physiologists term fissiparous, and in exterminating one false opinion you may be hindering the growth of an uncounted brood of false opinions.