Chapter 37.—Use of Rhetoric and Dialectic. 55.  This art, however, when it is learnt, is not to be used so much for ascertaining the meaning as for setting forth the meaning when it is ascertained.  But the art previously spoken of, which deals with inferences, and definitions, and divisions, is of the greatest assistance in the discovery of the meaning, provided only that men do not fall into the error of supposing that when they have learnt these things they have learnt the true secret of a happy life.  Still, it sometimes happens that men find less difficulty in attaining the ob ject for the sake of which these sciences are learnt, than in going through the very intricate and thorny discipline of such rules.  It is just as if a man wishing to give rules for walking should warn you not to lift the hinder foot before you set down the front one, and then should describe minutely the way you ought to move the hinges of the joints and knees.  For what he says is true, and one cannot walk in any other way; but men find it easier to walk by executing these movements than to attend to them while they are going through them, or to understand when they are told about them.  Those, on the other hand, who cannot walk, care still less about such directions, as they cannot prove them by making trial of them.  And in the same way a clever man often sees that an inference is unsound more quickly than he apprehends the rules for it.  A dull man, on the other hand, does not see the unsoundness, but much less does he grasp the rules.  And in regard to all these laws, we derive more pleasure from them as exhibitions of truth, than assistance in arguing or forming opinions, except perhaps that they put the intellect in better training.  We must take care, however that they do not at the same time make it more inclined to mischief or vanity,—that is to say, that they do not give those who have learnt them an inclination to lead people astray by plausible speech and catching questions, or make them think that they have attained some great thing that gives them an advantage over the good and innocent.