So I've been reading through the Phaedo and have been thinking about Plato and have come up with a question, before I ask the question, I will give some background.

Plato's theory of the forms (as I understand it) is an attempt to explain why particular things all partake in the same universal (or have shared properties). An example question is "why is it that all dogs have roughly similar properties? What causes this to be the case?" The theory of forms explains this by positing a great number of theoretical and unobservable entities called forms. So for instance there is a form of dog. What exactly this form of dog is (or any of the forms for that matter) Plato does not say, but what he does say is that the form of dog is the casual force which makes all particular instances of dogs similar in properties.

Now with modern science, a genetic and evolutionary explanation is a much more commonly accepted explanation as to why dogs (and living things generally) have the same properties and features. Different genes and DNA give instructions to cells telling them which proteins to produce and how to organize themselves in order to create bigger structures. So because dogs have dog genes, a dog structure is produced. So genes are used to give the same explanation that forms do. They explain, for biological things, why those biological things have similar properties and characteristics.

So my question is generally this "why is it that a genetic / evolutionary explanation of similarities is better (if it is better at all) than Plato's explanation of forms being the casual agent in creating similarities between species?"

I think there are a few answers to this question and I would be interested in hearing what you all have to say, but I would also be interested in receiving some thoughts on whether: Answer 1: Explanations that do not posit unobservable entities are weaker theories than theories that posit observable entities.

This seems like it might be true but I can't say exactly why. Can anyone explain this to me in more detail?


3 Answers 3


Genetics doesn't really explain what Plato tried to explain with "forms", as a statue of a dog shares exactly zero genes with an actual dog, but it shares the same Platonic forms. So genetics and forms explain completely different things.

But Plato got this (and in fact pretty much everything else) backwards. The answer to "Why does all dogs (including statues of dogs) have universal properties" is "Because we call the things with those properties 'dogs'". The "forms" are just human-created categories and have no existence outside our minds.

In other words, he got the cause and effect backwards. He wanted to know what cause all dogs to share properties, while the answer is that whatever shares these properties are called dogs.

See Nominalism.

So neither Platos realism, nor genetics is the correct answer to the question Plato tries to answer. Genetics is however the correct answer to another question: Why do living things that are related resemble each other. But that is a wildly different question from the one Plato failed to answer (although it is the question you try to answer, if I understand you correct).

  • But doesn't Plato deny that artifacts have the forms as their casual force? I think Plato say that a dog statue's cause was a human's attempt to imitate a form, the form of dog itself had no casual role to play in the creation of the statue. If this is the case then genetics and forms still play the same explanatory role in describing dog universals.
    – jay.guy
    Commented Jul 20, 2011 at 17:57
  • @jay.guy: I must have missed that part, but I don't think it fundamentally changes the argument, as his forms definitely are not restricted to animals, but mountains and colors and also made things (I seem to remember tables being mentioned, but I don't know if Plato himself did that). Commented Jul 20, 2011 at 19:11
  • @LennartRegebro: Yes, they are definitely not limited to animals or living things. +1 Excellent answer.
    – Cerberus
    Commented Jul 23, 2011 at 4:35
  • I don't know why I was thinking that forms don't apply to artifacts. You're both right that they do.
    – jay.guy
    Commented Jul 23, 2011 at 21:22

I think that reason why Plato's theory of the forms has been, to say, dismissed, is to be found in one of the premises of science: Falsifiability. That is to say, something is true (or considered so) as long as there be one of the two which follows: A formal demonstration has proven the object taken in analysis to be valid, repeated observations have shown that the object is valid during all observed instances.

Generally speaking, the former bases itself on axioms, which are automatically considered "valid" and are the premises of subsequent reasoning. These are especially common, as to give an example, in Mathematics, where "irrefutable starting points" form the building ground for all other theorems. Eg: Can we prove that numbers are infinite? No, we can't, but we generally consider them to be as to serve our purposes. On the other hand, we can't prove numbers aren't infinite either, but this isn't relevant to what concerns our learning. What we are interested in is that we can take any arbitrary value and make it as high or low as we want to.

The second case, on the other hand, is based on pure observation. Whereas the first case accepted an array of axioms to prove its point, hence could result in "final" conclusions, this second method cannot reach such a level of certainty due to the lack of a "general theorem". In fact, this type of analysis generates "theories", such as gravity. There is no formal proof for gravity, which is why we call it "the theory of gravity". That is because, due to the lack of fixed started points, we can only limit our conclusions to "all that has been so far observed".

This second type of analysis, that of empirical sciences, states that something is true so long as it is not proven false. (Again, falsifiability.) Plato's theory has been discarded because an apparently more accurate theory (Or rather, theories), described within the field of genetics and microbiology has provided more convincing answers.

  • 1
    Just to clarify, you certainly can prove that the set of numbers is infinite. It consists of showing exactly what you said, that given any number you can always get another bigger one.
    – Mitch
    Commented Jul 19, 2011 at 22:16
  • I don't fully agree... Might it not be that an "upper bond" of numbers does exist, except we cannot conceive it?
    – max0005
    Commented Jul 20, 2011 at 14:15
  • I claim you cannot give an upper bound to natural numbers. Suppose you claim you have one, call it x. I think it is undeniable that x+1 is also a natural number which is also bigger than your x, so x cannot be an upper bound. No matter what you do, there's always a bigger natural number. Therefore there is no upper bound. You might disagree, but then we'd be talking about different things then.
    – Mitch
    Commented Jul 20, 2011 at 14:43
  • 2
    There is a very small set of philosophers of mathematics called 'ultrafinitists' who go in the direction you allude to (something like 'we can only prove existence of numbers those we can fully construct mentally'), but they are very rare and are well outside of the mainstream of FOM (foundations of mathematics); they deny the applicability of many rules of inference (induction, p or -p, --p = p, etc). You can doubt anything in math just to see what the consequences are, but then you'll throw out a lot that is useful and consistent.
    – Mitch
    Commented Jul 20, 2011 at 14:51
  • Well... I know this sounds absurd, but what evidence do we have that that their thesis is wrong? Do we have any theorem whihc proves that numbers are infinite, hence, potentially exceeding our capacity to construct them?
    – max0005
    Commented Jul 20, 2011 at 18:44

Plato, with his forms, recognized similarities within his environment.

In my view, the forms are the ancestors of our mathematical models or patterns. He could not modelize with a computer the dogs and their general structure but he had the notion that if all the dogs shared similarities, then those similarities would have been cause by something, in his opinion, the abstract forms which must really exist somewhere because the dogs were really similar.

Plato was just acknowledging real causes of the dogs resemblances, and he was right. There are real causes of the similarities of the dogs, and it is indeed their genome which share the "dog" structure.

To answer your question: The genetic explanation is better because it is more precise of the general structure of the dog. It is more precise because we know how to control some of those genes if we want in order to create a different dog, as opposed to Plato who couldn't directly experiment with that (only in his head).

But Plato was not wrong in my opinion and his form theory is the nascent theory of mathematical abstract models.

  • But Plato claimed his forms not only had an actual existence, not as models, but as a more real and something perfect. I think you have misunderstood Plato in your effort of trying to fit him into the modern world. Mathematical models are not more perfect than reality, they aim to model reality as closely as possible. It's similar to mathematical abstractions, sure, in the case of a triangle etc, and that probably was the inspiration. But that doesn't make it less wrong... Commented Jul 20, 2011 at 19:13
  • @Lennart Regebro - But I think models have as much real existence as any representation you can make of any "real" object. The visual or touch you can get from any actual thing is just information processed by your brain. The real thing is infinitely different from what you can perceive, thus the difference between pure computer model or brain model of real stuff is fuzzy. Commented Jul 20, 2011 at 19:34
  • Do you think a mathematical model of a weather system is more real than the actual weather system, just because the actual weather system is more complex and less "perfect"? Commented Jul 20, 2011 at 19:37
  • Your 'actual' weather system is only what your senses transmit to your consciousness, and they pass only an elaborate model to your brain. It's not a matter of perfection but signal resolution, bandwith etc. Commented Jul 20, 2011 at 19:52
  • Geoffroy: So? You didn't answer the question. Is the model more real because it is more "perfect" (ie each raincloud looks exactly the same)? Commented Jul 20, 2011 at 20:01

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