It appears to me that the Greeks have laid down, with unique judgement, in the definition of art that it must have some usefulness for life. For all arts are tools for either preserving private life or for ruling the state. There is no need for expounding the individual arts here, or for showing the use for which they were invented and transmitted with great care from the elders to posterity. Rather it is necessary to exhort those who enter upon these studies of literature to consider at the beginning what the goal of these arts is, what benefit is to be derived from them, so that those who know may recognise the power and dignity of the arts more clearly, and choose more carefully the one that is most profitable to learn. They never achieve the perfect teaching whose minds do not look out for the certain goal of their studies, and they wander at random and without order or reason from one discipline to the other. ‘An art is the compound of concepts practised for some useful purpose in life’ (Technē esti systēma enkatalēpseōn engegymnasmenōn pros ti telos euchreston tōn eni tōi biōi) [Galen, Medical Definitions xix.350]; it is proved from the definition of art itself that the goal or benefit in all arts has to be envisaged from the beginning. This was also the reason why Quintilian searched for the purpose of rhetoric with such great care in chapter eighteen of book two.