Plato now presents this same definition to the opposite class of philosophers: to the Idealists, or partisans of the incorporeal--or of self-existent and separate Forms. These thinkers drew a marked distinction between the Existent and the Generated--between Ens and Fiens--[Greek: to\ o)\n] and [Greek: to\ gigno/menon]. Ens or the Existent was eternal and unchangeable: Fiens or the Generated was always in change or transit, coming or going. We hold communion (they said) with the generated or transitory, through our bodies and sensible perceptions: we hold communion with unchangeable Ens through our mind and by intellection. They did not admit the definition of existence just given by Plato. They contended that that definition applied only to Fiens or to the sensible world--not to Ens or the intelligible world.[105] Fiens had power to act and be acted upon, and existed only under the condition of being so: that is, its existence was only temporary, conditional, relative: it had no permanent or absolute existence at all. Ens was the real existent, absolute and independent--neither acting upon any thing nor being acted upon. They considered that Plato's definition was not a definition of Existence, or the Absolute: but rather of Non-Existence, or the Relative. [Footnote 105: Plato, Sophist. p. 248 C.] [Side-note: Plato argues--That to know, and be known, is action and passion, a mode of relativity.] But (asks Plato in reply) what do you mean by "the mind holding communion" with the intelligible world? You mean that the mind knows, comprehends, conceives, the intelligible world: or in other words, that the intelligible world (Ens) is known, is comprehended, is conceived, by the mind. To be known or conceived, is to be acted on by the mind.[106] Ens, or the intelligible world, is thus acted upon by the mind, and has a power to be so acted upon: which power is, in Plato's definition here given, the characteristic mark of existence. Plato thus makes good his definition as applying to Ens, the world of intelligible Forms--not less than to Fiens, the world of sensible phenomena. [Footnote 106: Plato, Sophist. p. 248 D. [Greek: ei) prosomologou=si tê\n me\n psuchê\n ginô/skein, tê\n d' ou)si/an gignô/skesthai . . . Ti/ de/? to\ ginô/skein ê)\ gignô/skesthai phate\ poi/êma ê)\ pa/thos ê)\ a)mpho/teron?]] The definition of _existence_, here given by Plato, and the way in which he employs it against the two different sects of philosophers--Materialists and Idealists--deserves some remark. [Side-note: Plato's reasoning--compared with the points of view of both.]