Respecting the first, Plato says that they must after all be ashamed not to admit, that justice, intelligence, &c., are something real, which may be present or absent in different individual men, and therefore must exist apart from all individuals. Yet justice and intelligence are not bodies. Existence therefore is something common to body and not-body. The characteristic mark of existence is, power or potentiality. Whatever has power to act upon any thing else, or to be acted on by any thing else, is a real Ens or existent something.[103] [Footnote 103: Plato, Sophist. p. 247 D-E. [Greek: le/gô dê\ to\ kai\ o(poianou=n kektême/non _du/namin_, ei)/t' ei)s to\ poiei=n e(/teron o(tiou=n pephuko\s ei)/t' ei)s to\ pathei=n** kai\ smikro/taton u(po\ tou= phaulota/tou, ka)\n ei) mo/non ei)sa/pax, pa=n tou=to o)/ntôs ei)=nai; ti/themai ga\r o(/ron o(ri/zein ta\ o)/nta, ô(s e)/stin ou)k a)/llo ti plê\n _du/namis_.]] [Side-note: Reply open to the Materialists.] Unfortunately we never know any thing about the opponents of Plato, nor how they would have answered his objection--except so much as he chooses to tell us. But it appears to me that the opponents whom he is here confuting would have accepted his definition, and employed it for the support of their own opinion. "We recognise (they would say) just men, or hard bodies, as existent, because they conform to your definition: they have power to act and be acted upon. But justice, apart from just men--hardness, apart from hard bodies--has no such power: they neither act upon any thing, nor are acted on by any thing: therefore we do not recognise them as existent." According to their view, objects of perception acted on the mind, and therefore were to be recognised as existent: objects of mere conception did not act on the mind, and therefore had not the same claim to be ranked as existent: or at any rate they acted on the mind in a different way, which constitutes the difference between the real and unreal. Of this difference Plato's definition takes no account.[104] [Footnote 104: Plato, Sophist. p. 247 E. [Greek: to\ kai\ o(poianou=n kektême/non du/namin], &c.] [Side-note: Plato's argument against the Idealists or Friends of Forms. Their point of view against him.]