Do unicorns exist in the mind? Do just a concept of unicorns exist in the mind? Or are unicorns a concept?

Anselm said God exists in the mind. But I wonder whether just a concept of God exists in the mind.

  • As you say, what exists in the mind is just ideas. Although when it comes to God there is some ambiguity because perhaps God is an idea, or the essence of God is present in ideas, or something esoteric like that. Unlike unicorns, which are definitely magical animals (if they were real), not ideas
    – causative
    Nov 30, 2023 at 6:35
  • @causative Then, animals can't be a concept?
    – user68943
    Nov 30, 2023 at 6:37
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    The concept of an animal can be a concept, but the concept of an animal is not the animal. Animals themselves cannot literally be concepts, though we might talk that way sometimes as a figure of speech.
    – causative
    Nov 30, 2023 at 6:48
  • @causative Thank you.
    – user68943
    Nov 30, 2023 at 6:48
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    I don't see this as a very useful question, it's just a matter of linquistics. The answer depends solely on how you define "exists", and either definition won't give you any new understanding of how the mind works. Nov 30, 2023 at 14:52

4 Answers 4


There is reasonable evidence that there are relatively dense, animated collections of molecules, light from which, upon entering your eyes, triggers chemical effects which propagate into your brain to cause mental states which you have learned to think of as 'seeing a horse'.

The dense animated collection of molecules can be considered the 'real' horse, and has certain inherent qualities which are independent of you. The mental experience you have when you look at the horse is just that- a mental experience, which should not be confused with the real horse itself.

When you stop looking at the horse, you can still imagine it, although your imagined image of it will not be as vivid, detailed or complete as the image that appeared in your mind when you looked at the real horse. Your brain is capable of recalling images of other horses, and of abstracting the idea of horses generally as an idea or concept, and to create imagined mental images of horses which need not correspond to any real horses but are just a creation of your mind.

Your brain can also imagine non-existent variants of horses, such a horses with horns, which you have learned to associate with the word unicorn. You can imagine an individual unicorn, with specific details, like its name, Zena, its colour, cherry pink, its especially soft and downy hair, or you can conjure up thoughts of unicorns in a more general sense, which is what we mean when we talk of the concept of a unicorn.

In summary, therefore...

'Real' horses exist as massive collections of molecules independently of you.

When you look at a real horse, your mind creates a vivid image of it.

Your mind can also conjure up vague images of horses, which need not correspond to 'real' horses, and hold more abstract thoughts about or related to the concept of horses.

Your mind can also conjure up images and other thoughts which are not about anything 'real', such as the rhinopus- the fabled hybrid of a rhino and octopus venerated by an ancient civilisation not yet known to science.

To draw a distinction between whether rhinopi exist in the mind or just the concept of rhinopi is rather false, since you cannot imagine an object as specific as a rhinopus without also having within your mind some structured thoughts related to rhinopi more generally, such as the possession of eight arms, the tendency to attack when threatened or annoyed, an outstanding inability to squeeze into crevices owing to the encumbrance of solid horn and so on.

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    "In our world," said Eustace, "a horse is a dense animated collection of molecules." / "Even in your world, my son, that is not what a horse is, but only what it is made of." :-) goodreads.com/quotes/…
    – LarsH
    Nov 30, 2023 at 15:33
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    @LarsH a great great comment! +1 Nov 30, 2023 at 15:56

Unicorns do not exist in the mind, because they do not exist at all.

The concept of an unicorn is a concept which exists in the mind.

Anselm in his famous attempt to prove the existence of god by an ontological argument starts from the concept of God as a concept in the mind. In this context he does not argue from a religious position like "God is in us".

  • Then, are imaginary friends just a concept?
    – user68943
    Nov 30, 2023 at 7:21
  • @Collins Yes, they are just a concept without referent. - You cannot rely on imaginary friends. Why not? Because they do not exist.
    – Jo Wehler
    Nov 30, 2023 at 7:41
  • Wait a minute. Unicorns are not a concept, but imaginary unicorns are a concept?
    – user68943
    Nov 30, 2023 at 7:46
  • @Collins There is difference between the word "friend" and the word "unicorn". The former has a referent, the latter does not have a referent. I consider both words to denote a concept. - But if it is clear what you mean, and as long as not running into linguistic traps, you may use the words with your favorite meaning. - If you say "Henry is my friend", then you use the word "friend" as a concept. Your statement expresses that the concept has at least one referent, namely Henry.
    – Jo Wehler
    Nov 30, 2023 at 8:02
  • Can I ask one more? Does a concept have color, shape, etc?
    – user68943
    Nov 30, 2023 at 8:07

You say :

Do unicorns exist in the mind?

Since the mind is that which thinks, imagines... it's obvious that unicorns exist in the mind.

But, in order to proceed forward, I will answer the question : "Do unicorns exist?".

Since the definition of "exists" may have different interpretations and the ontology of existence varies from person to person, we cannot have a definite answer.

According to Wikipedia :

  • Existence is the state of being real or participating in reality.
  • Reality is the sum or aggregate of all that is real or existent within the universe, as opposed to that which is only imaginary, nonexistent or nonactual. The term is also used to refer to the ontological status of things, indicating their existence.

From these definitions it follows that unicors do NOT exist, since they are imaginary.

But, by considering the concept "participating in reality" from the definition of existence, since we - humans - co-form reality, our imagination participates in the creation of reality too. If a sculptor constructs a unicorn isn't it real? So isn't a unicorn real, as a potential? as a contributing factor in our behaviour?

And, even in sciences, isn't behaviour of things, that which we study? Do we really have knowledge of anything else than how nature appears to us?


Technically speaking, yes, but it exists only as an object of thought and not as a subject, that is, as a substance in its own right. It is at most an accident inhering in you, the actually existing substance. However, common talk of something existing normally means only the latter sense of substantial existence, so unicorns strictly and colloquially speaking do not exist.

  • How much is accident, and how much is bad copying of medieval bestiaries? This is a unicorn, and the word is descendant from what Pliney the Elder called this animal: en.wikipedia.org/wiki/Rhinoceros#/media/…
    – Joshua
    Dec 1, 2023 at 3:09
  • @Joshua "accident" here means something inhering in a subject, not a chance happening. So the thought will be an accident inhering in you regardless if it corresponds to something with subsistence. Also, the signifier (the word "unicorn") may be the same between modern usage and Pliny's, but the signified (🦄/🦏) is not - that's a different (even if interesting) matter from OP's question, who certainly means 🦄 by the term.
    – Mutoh
    Dec 1, 2023 at 19:27

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