Abstract

After a re-consideration of the famous Growing Argument (raised by the Academics to deny the continuity of the identity through changes), the focus is set on the Stoic reply, based on the assumption that each individual has a peculiar quality, that ensures its permanence and its distinguishability from the other things. The «peculiarly qualified» (idiôs poion) has not only the ontological function of preserving the identity and the unicity of each being in the world, but it also plays a crucial epistemological role, making it possible to unambiguously identify the objects of our knowledge. Nonetheless, it is far from clear what the idiôs poion actually is. The Author of the paper proposes a revised version of Lewis’ interpretation, according to which the «peculiarly qualified» is a portion of pneuma, i.e. the corporeal principle of the Stoic physics. Matter, however, is not reducible to a mere amount of stuff: indeed it has coherence and permanence, although some quantitative properties change continuously through the addition or subtraction of substance.