Please be patient with me on this for just a little longer. What is at issue is whether talk in the Phaedo of 'true philosophers' and non-philosophers is consistent, nonetheless, with non-philosophers' having virtue but to a lesser degree. If it is, then it's not clear that the Phaedo and Laws are incompatible, as Bobonich claims.
Since virtue depends upon knowledge, according to the Phaedo, then, as an anonymous commentator has already pointed out, what is at issue is whether knowledge can differ in degree.
Yet Plato clearly allows that it can. Phaedo 66e-67a is perhaps the most important passage where he does so, but there are others besides:
It really has been shown to us that, if we are ever to have pure knowledge (kaqarw=j ti ei)/sesqai), we must escape from the body and observe things in themselves with the soul by itself. It seems likely that we shall, only then, when we are dead, attain that which our argument shows, not while we live; for if it is impossible to attain any pure knowledge (kaqarw=j gnw=nai) with the body, then one of two things is true: either we can never attain knowledge or we can do so after death. Then and not before the soul, is by itself apart from the body. While we live, we shall be closest to knowledge (e)gguta/tw e)so/meqa tou= ei)de/nai) if we refrain as much as possible from association with the body and do not join with it more than we must, if we are not infected with its nature but purify ourselves from it until the god himself frees us (Grube, 66e-67a).From this passage one might argue: If knowledge is by degree and approximation, and virtue is coincident with knowledge, then virtue apparently would vary in degree as well. Similarly, if it followed that someone had virtue in no degree, if he lacked a full grasp of the Forms, then everyone would lack virtue, even ostensible philosophers such as Socrates and his friends, since no one while living in the body has that sort of full grasp.
a)lla\ tw=| o)/nti h(mi=n de/deiktai o(/ti, ei) me/llome/n pote kaqarw=j ti ei)/sesqai, a)lla\ tw=| o)/nti h(mi=n de/deiktai o(/ti, ei) me/llome/n pote kaqarw=j ti ei)/sesqai, a)pallakte/on au)tou=+ kai\ au)th=|+ th=| yuxh=|+ qeate/on+ au)ta\+ ta\ pra/gmata+: kai\ to/te, w(j e)/oiken, h(mi=n e)/stai+ ou(= e)piqumou=me/n te kai/ famen e)rastai\ ei)=nai, fronh/sewj, e)peida\n teleuth/swmen, w(j o( lo/goj shmai/nei, zw=sin de\ ou)/. ei) ga\r mh\ oi(=o/n te meta\ tou= sw/matoj+ mhde\n kaqarw=j gnw=nai, duoi=n qa/teron, h)\ ou)damou= e)/stin kth/sasqai to\ ei)de/nai h)\ teleuth/sasin: to/te ga\r au)th\ kaq' au(th\n h( yuxh\ e)/stai xwri\j tou= sw/matoj, pro/teron d' ou)/. kai\ e)n w(=| a)\n zw=men, ou(/twj, w(j e)/oiken, e)gguta/tw e)so/meqa tou= ei)de/nai, e)a\n o(/ti ma/lista mhde\n o(milw=men tw=| sw/mati mhde\ koinwnw=men, o(/ti mh\ pa=sa a)na/gkh, mhde\ a)napimplw/meqa th=j tou/tou fu/sewj, a)lla\ kaqareu/wmen a)p' au)tou=, e(/wj a)\n o( qeo\j au)to\j a)polu/sh| h(ma=j:
Seems like a closed case, doesn't it?
But these implications are perhaps avoidable. It may just be possible to allow degrees of knowledge but draw a sharp distinction between philosophers and others nonetheless, as I'll explain in a subsequent post.