What is meant by the behavior of other people in argument?

Here it is said that the simplicity of the explanation is decisive in choosing the best explanation.

Solipsism has fewer entities(only my mind), so why isn't it simpler explanation?

  • 1
    If everything is produced by my (subconscious?) mind, then either that explains everything trivially (my mind is causing everything) or explains (almost) nothing by way of undermining the concept of explanation in the first place. The SEP article on theoretical simplicity notes that it's less "fewer objects" and more "fewer properties" that lends itself to the simplicity at issue (to be fair, though, it is common enough to ask about quantitative instead of qualitative simplicity). Commented Aug 2, 2023 at 14:17
  • yeah so what is solipsism meant to explain? if you find (only) you can perform miracles at will, you might want to explain that with solipsism. but it doesn't obviously explain the existence of other humanoid bodies. the problem with evil daemons is, as @KristianBerry suggests, that it can explain anything and in the process nothing
    – user67104
    Commented Aug 3, 2023 at 7:08
  • Next we explain how my mind produces a universe. Simplest explanation? I am God, of course. Reductio ad absurdum is the equally simple refutation of simple explanations. Explanatory power is good, too.
    – Scott Rowe
    Commented Aug 3, 2023 at 11:37
  • How do you explain your birth (thence birthday, parents etc) from a solipsistic starting point?
    – Rushi
    Commented Aug 3, 2023 at 13:43
  • IBE does not "arrive" at which explanation is the best, it presupposes that the bestness was "arrived" at by some other means. How is not the business of IBE. "Simplicity" is only one version of such means, and the number of "entities" is only one way to 'measure' simplicity, see SEP, Simplicity. Many would argue that solipsism does not even qualify as a plausible explanation, let alone the "simplest", and let alone the "best" one.
    – Conifold
    Commented Aug 3, 2023 at 17:16

3 Answers 3


In terms of Occam's Razor, the principle that the simplest explanation is often the best, it's important to remember that 'simplest' doesn't mean 'most minimal.' It means the explanation that makes the fewest assumptions while still accounting for all the facts. In that sense, the existence of other minds is a far simpler—and more useful

Because solipsism fails to account for the complexity and richness of our experiences. If we are the only conscious entities, how do we account for the diversity and unpredictability of the world around us? Are we to believe that we are dreaming up every blade of grass, every book we read, every conversation we have? In contrast, the idea that other minds exist—while it may be more 'complex' in that it posits the existence of billions of individual consciousnesses—actually offers more explanatory power.

  • Solipsism: Has fewer entities (only one conscious mind) Has many explanations (my mind is responsible for my behavior, my subconscious is responsible for the behavior of other people). Solipsism will always have fewer entities, so it will always be simpler if we judge by the number of entities.
    – Johnny5454
    Commented Aug 2, 2023 at 14:31
  • Existence of other minds: Has many entities (billions of conscious minds) Has fewer explanations (all people have minds that are responsible for their behavior) The existence of other minds will always have fewer explanations, so it will always be a simpler explanation if we judge by the number of explanations. So what is easier?
    – Johnny5454
    Commented Aug 2, 2023 at 14:31
  • 1
    In other words, it's more complicated to explain why you're the only mind, than it is to count yourself one among many. Solipsism, for instance, invalidates evolution.
    – J D
    Commented Aug 2, 2023 at 14:33
  • 1
    So the best explanation for other people's behavior is that other people have minds. This explanation is the simplest, it is consistent with our everyday experience and scientific facts.
    – Johnny5454
    Commented Aug 2, 2023 at 14:53

This page (from an open source book, not a published article: it's just meant as illustrative here) says there are "Seven Explanatory Virtues"

Explanatoriness... Depth... Power... Falsifiability... Modesty... Simplicity... Conservativenes

I've seen lists before that include 'depth' and 'power', and the descriptions all appear to make intuitive sense.

Lipton (a philosopher of science) lists "mechanism, precision, scope, simplicity, fruitfulness, and fit with background beliefs", which make an explanation "lovelier"

Simplicity is not the only "explanatory virtue"


The "best explanation" may be one that:

  • Avoids the addition of unnecessary claims that have no explanatory or predictive power.
  • Doesn't have comparable alternative explanations (e.g. it was a ghost, or it was fairies, or it was a god, or it was...).
  • Aligns well with our current demonstrable understanding of reality (if your explanation requires that gravity stopped working, or causality broke, that's not a great explanation). Our current understanding of reality may be wrong, so this isn't an automatic disqualifying criterion, but it does mean we should favour explanations that fit with our current understanding of reality, as has been demonstrated.

As for metaphysical solipsism (i.e. the self is the only existing reality), that involves an entirely unnecessary additional model of reality.

You are observing this reality, so it must exist in some form, even if only in your mind.

If you reject solipsism, that's the only reality that you accept.

If you accept solipsism, you're adding some additional model of reality on top of that: that you exist somewhere, somehow, that isn't in the reality you perceive. That's a superfluous claim, that we have no evidence for, and which has no explanatory or predictive power.

So the best explanation would be to reject solipsism.

If you go down the path of trying to figure out how you came to perceive what you do, solipsism may seem simpler, but this is mostly just kicking the can down the road: it's easy to say that what you perceive came about from your mind, but now you have to explain how your mind came about, and in what form it even exists, and how such an existence is possible, and what evidence it's supported by, and why your mind generated what you perceive in the way that it did, and how you dismissed other possible comparable alternative explanations.

  • Why is the existence of other minds the best explanation for other people's behavior? How did IBE come to this conclusion?
    – Johnny5454
    Commented Aug 3, 2023 at 8:53
  • @Johnny5454 If you accept the existence of perceived reality, as the best explanation, then you can accept the existence of other minds on the basis that you have a mind, and other people look like you and behave like you do (similar to what was said in an answer to a different question of yours).
    – NotThatGuy
    Commented Aug 3, 2023 at 10:19
  • In order to accept the existence of external reality, I have to come to the conclusion that this is the best explanation. How do I do this? Who decides all this? Professional philosophers or each person must work it out for themselves, or is there some general principle?
    – Johnny5454
    Commented Aug 3, 2023 at 11:02
  • @Johnny5454 I expanded on my answer. In general, you can evaluate all the methods, explanations and arguments that have been presented and come to your own conclusion. You could potentially also defer to the judgement of philosophers. Although I'm not sure that there is really a consensus about much in philosophy, and this wouldn't really work for the existence of external reality, because to accept the judgement of philosophers, you first have to accept that they exist (unless perhaps you hold that they're a part of your mind that's been reflecting on that topic).
    – NotThatGuy
    Commented Aug 3, 2023 at 13:12
  • So I have to decide for myself which explanation is the best and easiest, and then stick with that explanation? If we rely on the opinions of philosophers, will it be circular reasoning? So in the case where solipsism has fewer entities and the existence of other minds has fewer explanations, only I can determine which explanation is simpler for me?
    – Johnny5454
    Commented Aug 3, 2023 at 13:52

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