I probably incorrectly understand some basic things, so I'll show my layman thinking process for easier identification of where lies the problem.

Let's start with basic dichotomy - materialism vs. idealism of what's more primal - matter or mind. As far as I understand, idealism operates only on concepts of human mind and perception thus it's strictly anthropocentric approach.

As materialism states that only matter ontologically exists, idealism states that only ideas (i.e. human cognitive apparatus and perception) ontologically exist.

Thus if we want to stick with idealism, we fall into correlation loop - we are constricted by the ideas we are able to think, as if we assume something that we can't think, it automatically becomes thinkable.

So if idealist wants to say that some object "exists" that would mean something like "we are able think that this object exist (exist in intersubjective consensus reality)".

Then Plato's states his Forms - entities that are not material objects (thus, it's not a materialism), but also not a results of human mind, as they ontologically exist, independent from our cognition. So why is it idealism? Forms doesn't fall in any category of mind and matter. Is it implicitly assumed that Form are results of human cognition? In another words, who thinks the Forms for them to exist in idealistic approach?

As far as I understand, by Plato "actual" reality constitutes only from Form, by they are inaccessible by any meaning. Would it be correct to say that the Form might as well not exist at all from this standpoint?

Why does Platonism falls into a mathematicism category? If we say that everything is math concepts, not correlated with human perception and cognition, wouldn't it be a materialism?

  • "Idealism operates only on concepts of human mind and perception thus it's strictly anthropocentric approach" is incorrect. Idealism claims that mind/ideas are the primary mode of being contra materialism, but this mind does not have to be human or human-related, human mind is just an example most familiar to us. Just as solids and liquids are the most familiar kinds of matter, but there are plenty of others, gases, plasmas, fields, dark matter, etc. Plato's ideas are completely human-independent and self-sufficient, so his idealism is as objective as typical materialism.
    – Conifold
    Commented May 22, 2020 at 23:11
  • I would not use materialism but use appearance. Think of essence (Idea) [fixed] and appearance [changeable].
    – Gordon
    Commented May 22, 2020 at 23:13
  • In addition, “Theory of Forms” en.m.wikipedia.org/wiki/Theory_of_forms
    – Gordon
    Commented May 23, 2020 at 0:14
  • A discussion of the different ways "idealism" has been used to describe both Greek/European and Buddhist and Hindu philosophies and religious views: web.archive.org/web/20100314020538/http://kelamuni.gaia.com/…
    – Hypnosifl
    Commented May 23, 2020 at 10:06
  • 'As far as I understand, by Plato "actual" reality constitutes only from Form' -- I don't think he saw the material world as an illusion that doesn't exist at all, more that it's less good, or less worthy of our attention, than the world of Forms. Plato's Timaeus features a kind of divine craftsman who shapes the world of matter by copying the world of Forms, for example. The hints about his unwritten philosophy may also be relevant to how he thought of the relation.
    – Hypnosifl
    Commented Jun 23, 2020 at 18:36

1 Answer 1


As the term 'idealism' is used in epistemology and metaphysics there is nothing common and distinctive to all forms of idealism except the claim that reality is non-physical. This accommodates Berkeleley's view that all that exist are immaterial minds and their ideas. It also fits with Plato's theory of Forms, where the Forms are pure essences (e.g. the Form of the Beautiful is alone really beautiful) transcendent of the physical world although the physical world 'participates in' or 'imitates' the world of Forms.

Mathematical 'platonism' holds that immaterial mathematical objects such as numbers and sets exist independently of the human mind. (Apologies to mathematicians, who can state it better.)

Your question raises the whole issue of the role of classifications ('labels') in philosophy: idealism, empiricism, realism, antirealism, pragmatism, conceptualism, &c. I think it is far better to establish what a philosopher holds exactly than to see what classificatory box s/he fits into. Boxes suppress differences: for instance Locke, Berkeley, and Hume are standardly put into the box marked 'empiricism' yet this conceals points of wide, even vital, difference between them. Locke recognised a physical world of primary qualities; Berkeley denied it in any sense Locke would have acknowledged. Berkeley has to do double duty in the box marked 'idealism' as well as 'empiricism' yet there is no significant similarity between Berkeleian idealism which posits God, mind or spirits, and their ideas, and Platonic idealism posits a transcendent world of pure essences.

  • Sorry for a bit of long response. As you say it's more of a labeling problem, how strictly Plato's ideas falls into idealism category? More general question: what aspect is more important in definition of idealism - that ideas have ontological existence or that only human cognition exists? Regarding Plato's Forms - if I understand correctly, it is stated that Form are not accessible by any means. Using reduction, would it be correct to say that Forms only exist in our cognition or, even more strict, that they do not exist ontologically at all?
    – ᾯᾯᾯ
    Commented Jun 7, 2020 at 1:58
  • I better re-word my question about mathematical monisms as idealism subset - if we say that only math entities are ontologically exist, wouldn't it be equivalent to say that they are in fact material objects?
    – ᾯᾯᾯ
    Commented Jun 7, 2020 at 2:02

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .