Can we say that beings are different precisely because this being has this potencies and that being has that potencies? Is the (only) thing differentiating two different things their set of potencies? For example is only that which is differentiating dog from me that dog has different potencies then I have? If yes, how do we have different potencies? Dog can be destroyed into something and that something be used to create human being and therefore dog is potentialy human being, but then, dog is potentialy everything that human is potentially?

If no, how come things are diverse and what is solution to Parmenides's monism? Do two human beings have same potencies, if yes how then are they different? If no, how come one person has capacity to understand something that others do not have capcity to understand (for exmaple, only some people can understand math while others can not). Or how come one person has potency to play piano while others do not have that potency?

  • Actuality and Potentiality is a key deistinction in A's Metaphysics : "Consider a piece of wood, which can be carved or shaped into a table or into a bowl. In A’s terminology, the wood has two different potentialities, since it is potentially a table and also potentially a bowl. The matter (the wood) is linked with potentialty; the substance (the table or the bowl) is linked with actuality. The as yet uncarved wood is only potentially a table, and so it might seem that once it is carved the wood is actually a table." Jan 16, 2019 at 10:56
  • It seems obvious that Parmenides view allows for the multiplicity of the world since this is what it is supposed to explain. His idea is seen properly developed in mysticism and the Perennial philosophy and there is no way to 'dispel' this. Perhaps Parmenides did not develop his idea well enough to convince you but the Unity of All is not an idea that can be refuted or falsified. It's not monism,and I'm not sure Parmenides view is either, but that's another issue. I feel the rejection of Parmenides is a mistake with consequences still being suffered by scholastic philosophy.
    – user20253
    Jan 16, 2019 at 12:17
  • A's metaphysics is not simple (and I'm not an expert...). Basically, the pair actuality-potentiality maps "dinamically" the pair matter-form. Form is the "essence" and thus it is common to all individual of the same ... kind, species, etc. Thus, the burden of "individuality" is on matter. If so, in your example, we have to say that all human have the same "potential intelligence" and only the "incarnation" of form into matter (and maybe environment and education ?) are responsible for the "actual performance". Jan 16, 2019 at 15:33
  • @Thom - We cannot get into this here, but a fundamental theory must reduce change and multiplicity along with time and space. So whatever we think of Parmenides we have to end up pretty much where he ended up, with the metaphysical unreality of change and things that change, or indeed 'things; of any kind. .
    – user20253
    Jan 16, 2019 at 15:49

3 Answers 3


You're asking quite a few questions here, but the at the root it seems you're asking about the principle of individuation, i.e., What makes something an individual? What makes this dog different from that dog?

St. Thomas Aquinas (De Ente et Essentia chap. 3) argues that the principle of individuation is "materia signata quantitate" ("matter signed with quantity" or "signate matter"), whereas Scotus (Opera Omnia, Opus Oxoniense II dist. 3 quaest. 6.) thought it was an accidental form called haecceity ("this-ness," from the Latin hæc = "this").

See the first article "On the principle of individuation" of Hugon's Cosmology (pp. 295-307 = PDF pp. 303-315).


Parmenides developed an argument that forced his interlocuters to grapple with the problem of change. So far from 'dismissing' Parmenides they were taking him seriously. There are two main attempts:

a. atomism, developed by Democritus and Leucippus.

b. actuality/potentiality, developed mainly by Aristotle.

There are modern revivals of both, the former in atomic theory of matter whose current avatar are the quark/leptonic model of the standard model; and the latter in quantum mechanics where the wave function represents potentiality and change; and measurement, actuality.

  • Before jumping all the way to quanta. i would note that Newtonian physics adds something really important to your option b, that Aristotle left out: The notion of continuous, derivative potentials like the moment of inertia or the potential energy granted by height. Newton's concept of 'fluxions' is his solution to Zeno.
    – user9166
    Jan 16, 2019 at 21:54

Your proposal is exactly Aristotle's alternative to Parmenides's flat, actualist understanding of being, "never shall this be proved that things that are not, are", that landed him with collapsing everything unto the One. For there can be no passage from one to many. It is still reflected in, predominantly extensionalist, modern interpretations of modal logic in terms of possible worlds, that simply posit many side by side. For modern exponents of Aristotle's view see How does the concept of the 'virtual' (Deleuze) relate to 'counterfactuals' (Lewis)? Lewis advocates the more common modern solution that replaces potencies with counterfactuals, sentences about what is not, but might have been. In another world, as flat as Parmenides's. It is not so much a solution as a workaround, we get to talk about capacities as alternative actualities, but not to explain how they are present here and now, as potencies. Here is from Felt's Impossible Worlds:

"The shadow of Parmenides seems to lie over these discussions. For whether with Lewis one takes possible worlds to be as real as the actual, or one tries to replace them solely by the actual, the upshot seems the same: all is reduced to a planar understanding of what it means to be. In these controversies the anti-Parmenidean (Aristotelian) notion of potentiality, as an intrinsic character of the actual, has tended to be supplanted by possibilities (in the plural)...

[...] The link between Actuality and Possibility lies not in possibilities but in potentiality. This potentiality is grounded in the actuality of the settled past and in the dynamic actuality of present process. Thus the new actual is always growing out of the womb of the potential, but the potential is itself rooted in and structured by past actuality.

The actualists are therefore right in denying an independence to the possible. On the other hand, to be potentially is really a way to be, even though it is not to be actually. And this of course is just what Aristotle said in response to Parmenides, who conceived of only one way of being, being in actuality."

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