Hence its comprehensive scope and its authority. There is further important respect in which moral knowledge is differentiated by Socrates from the knowledge belonging to professional skills. The importance of this distinction is that it serves to emphasize Socrates' belief that knowledge of the good is not only necessary but also a sufficient condition for the attainment of happiness. Socrates also considers the relations between ability, knowledge, goodness, and desire in their application to the practice of professional skills. To know whether there are the same relations between them in their application to moral behavior is to first establish that ability implies knowledge, and that in any professional skill the able man is a good man.
Ability here mean ability to achieve one's aim, to succeed in what one wishes to do.
Given the aim, the good man is able to achieve it. If the kind of connexion between ability and knowledge which exists in professional skills existed in moral behavior, it would follow that moral knowledge is a necessary and sufficient condition of ability to achieve one's aim. Here, the analogy between moral knowledge and the knowledge belonging to professional skills breaks down. If in this respect they were the same, it would be necessary to conclude that, just as in the practice of professional skills it is only able and hence knowledgeable and good man who deliberately gives bad performances, so in moral behavior it is only the knowledgeable and good man who deliberately does wrong. In this respect the morally good man is capable of deliberate wrongdoing, while the wrongdoing of the morally wicked man is always involuntary.