Plato, Republic

[353a] you could use a dirk to trim vine branches and a knife and many other instruments.” “Certainly.” “But nothing so well, I take it, as a pruning-knife fashioned for this purpose.” “That is true.” “Must we not then assume this to be the work or function of that?” “We must.”

“You will now, then, I fancy, better apprehend the meaning of my question when I asked whether that is not the work of a thing which it only or it better than anything else can perform.” “Well,” he said, “I do understand, and agree [353b] that the work of anything is that.” “Very good,” said I. “Do you not also think that there is a specific virtue or excellence of everything for which a specific work or function is appointed? Let us return to the same examples. The eyes we say have a function?” “They have.” “Is there also a virtue of the eyes?” “There is.” “And was there not a function of the ears?” “Yes.” “And so also a virtue?” “Also a virtue.” “And what of all other things? Is the case not the same?” “The same.” “Take note now. Could the eyes possibly fulfil their function well [353c] if they lacked their own proper excellence and had in its stead the defect?” “How could they?” he said; “for I presume you meant blindness instead of vision.” “Whatever,” said I, “the excellence may be. For I have not yet come¹ to that question, but am only asking whether whatever operates will not do its own work well by its own virtue and badly by its own defect.” “That much,” he said, “you may affirm to be true.” “Then the ears, too, if deprived of their own virtue will do their work ill?” “Assuredly.” “And do we then apply [353d] the same principle to all things?” “I think so.” “Then next consider this. The soul, has it a work which you couldn't accomplish with anything else in the world, as for example, management, rule, deliberation, and the like, is there anything else than soul to which you could rightly assign these and say that they were its peculiar work?” “Nothing else.” “And again life? Shall we say that too is the function of the soul?” “Most certainly,” he said. “And do we not also say that there is an excellence virtue of the soul?” [353e] “We do.” “Will the soul ever accomplish its own work well if deprived of its own virtue, or is this impossible?” “It is impossible.” “Of necessity, then, a bad soul will govern and manage things badly while the good soul will in all these things do well.²” “Of necessity.” “And did we not agree that the excellence or virtue of soul is justice and its defect injustice?” “Yes, we did.” “The just soul and the just man then will live well and the unjust ill?” “So it appears,” he said, “by your reasoning.”