[18] For as it is of no use to study music in an unmusical manner, nor grammar without any attention to its true principles, nor, in short, any art whatever in a manner either devoid of art or proceeding on false rules of art, but [19] [20] each art must be cultivated on a strict obedience to its rules; so also it is of no avail to apply one’s self to the study of wisdom in a crafty spirit, or to the study of temperance in a nigardly and illiberal frame of mind, nor to courage rashly, nor to piety superstitiously, nor, in fact, to any other science which is in accordance with virtue in an unscientific manner. For all these steps are confessedly erroneous. In reference to which, a law has been delivered to us "to pursue what is just in a just manner," [21] that we may cultivate justice and every other virtue by those works which are akin to it, and not by those which are contrary to it.