Do solipsism and the theory that the external world is real have equal explanatory value?

Question

Given a recent question just asked in regards to whether or not Occam's razor supports solipsism, I thought it would be prudent to ask whether the explanatory value of both theories (solipsism vs. the external world being real) are equal.

To make things a bit more interesting, let's assume that under a solipsistic theory, our experience follows certain laws, which happen to be the same laws in physics.

Thus, in order to generate our conscious experience, certain laws and initial conditions are all that is needed to predict the forthcoming parts of our subjective experience.

Now, in order to generate the events of the real world under the theory that the external world is real, the same laws and initial conditions are all that is needed to predict the events of the universe.

Thus, can't one argue that the explanatory power of both theories are actually the same, contrary to the notion that solipsism has inferior explanatory power? If someone retorts and asks "what generates our conscious experience in solipsism? It seems to come from nowhere.", the same can be asked for the theory that the external world is real. As far as we know, we do not actually have an explanation for what generates our conscious experience in the traditional, materialistic view of the world.

So again, is there a difference in explanatory value between solipsism and the theory that the external world is real? Or not?

EDIT:

One thing I can think of from a pro materialist view is that it may make no sense for laws to operate on an immaterial reality. What are the laws acting upon if there is no ontological difference between components of experience?

Answer 1

No. What you seem to be suggesting is that you might make an assumption that your individual mental sensations are governed by some set of rules that ensures that the events you, the solipsist, imagine in your head evolve in the same way as events I, the non-solipsist, perceive in the real world. The difference, of course, is that you cannot say what the rules are. I can say what many of the rules are in the real world, and I can see why certain patterns I perceive are the result of other influences. You cannot specify what the corresponding solipsistic rules are- you can only hypothesise that they exist, which is no explanation at all. You might just as well say that an omnipotent invisible pink rabbit is the cause of everything.

Also, the rules that govern the real world only make sense in the context of there being a real word. For example, there are many factors at play that have lead to millions of people communicating in mandarin, a language I do not understand. I would challenge you to provide a convincing explanation of why and how your brain would create the experience of a world in which millions of people seemed to communicate effectively in a language your brain does not appear to understand. Simply assuming that there is some set of rules to account for it is hardly an explanation.

EDIT

Solipsism has no explanatory power in relation to the acquisition of knowledge. In the real world, I experience many things that I do not understand. To take the example in the comments, I experience computers performing rapid calculations that would take me days to perform long-hand. I have no idea how the computer works. I can discover how it works by looking at information produced by other people. More generally, my explanation for how I, in the real world, possess knowledge, is that I have gained it over the course of my life, benefitting from the knowledge of others. I have not studied the algorithms that find the fourth root of a number, for example, but other people have, and I can read what they have written to acquire that knowledge. In my real world view, billions of humans have acquired knowledge and are able to share what they have acquired. How do you, the solipsist, explain that? How can you account for the fact that your mind is able to imagine a computer finding a fourth root of a large number, and yet you have no immediate idea of how it does so? It seems to me that you have to assume that the knowledge is all there in your head to begin with.

You also are suggesting that somehow the laws of physics might just as equally apply to your imagined solipsistic world. But the laws of physics require, for example, the conservation of energy, so how are you, as the solipsist, fuelled? What is your source of energy? Your imagined solipsistic experience is that you consume food. But according to you, the food does not exist.

It seems to me that you are trying to explain your solipsist's imagined world by analogy with my real external world, while denying that my world exists! You can't have it both ways.

Answer 2

In this answer, I’ll restate the comparison made in this chat discussion:

Option 1: Physicalism

Brute Facts

• Spacetime (and potentially several more dimensions)
• Physical laws
• Physical constants
• A huge amount of elementary particles
• Possible existence of a multiverse
• Anything else I'm probably forgetting.

Explanation of First-Person Experience under Physicalism
The explanation of first-person experience in physicalism is complex, especially due to the Hard Problem of Consciousness. Nevertheless, if we assume consciousness somehow emerges from matter (as posited by theories like type physicalism), subjective experience is explained as signals from the external world that are decoded and interpreted by the observer’s brain, changing in accordance with physical laws over time.

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Option 2: Metaphysical Solipsism (as suggested in chat)

Brute Facts

• This mind
• The present moment (with time as an illusion; only the present exists)
• Present experience of memories creating the illusion of time
• The contents of this mind (i.e., qualia) in the present moment

Explanation of First-Person Experience under Metaphysical Solipsism
Here, all conscious experiences are simply brute facts experienced by this mind in the present moment.

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Comparing the Two Worldviews

Both physicalism and metaphysical solipsism posit brute facts that resist further reduction. However, the version of metaphysical solipsism I suggest requires only a minimal set of brute facts to account for subjective experience in the present, where the past and future are illusory. Physicalism, by contrast, requires a more elaborate framework, including physical laws, fundamental particles, spacetime, and possibly multiple dimensions or universes.

In terms of explanatory power, both worldviews can more or less explain (or explain away) first-person subjective experiences, albeit with differing degrees of ontological complexity.

Answer 3

I consider neither solipsism nor the existence of an external world a theory. Both are hypotheses.

The latter is the basic hypothesis of science and also of our everyday understanding and acting. The former is the principle of a different worldview which may possibly be used to question science.

Science strives with some success to build a consistent theory which explains observations in different domains. But I have never met a proponent of solipsism who acts accordingly to their thesis. Hence solipsism lacks any consequence in action.

Answer 4

You ask:

Do solipsism and the theory that the external world is real have equal explanatory value?

Absolutely not. The theory that the external world is real has a name in modern discourse: scientific realism (SEP). Scientific realism is an extension of direct realism and takes human intuitions about reality and layers them with the sciences. The end result is that the modern scientific project explains a tremendous variety of phenomena, from the formal sciences which are mathematical and logical in nature, to the natural sciences, which describe physical, chemical, and biological objects and events. The social sciences explain minds and societies, imperfectly, but to a great extent. Solipsism, on the hand, is a minor hiccup in insights that direct realism has to contend with scientific instrumentalism, and that there is a difference between appearances and actuality. Sophisticated thinkers tend to contemplate solipsism in the same way as radical skepticism, and then reject it wholeheartedly as a philosophical dead end.

Answer 5

Do solipsism and the theory that the external world is real have equal explanatory value?

If solipsism is the belief that your own mind is the only reality, then the only thing to explain is your own mind.

Scientific explanations all involve entities distinct from anybody's mind, so a solipsist in this sense cannot completely accept any scientific theory. However, a solipsist could accept the form of scientific theories while rejecting their underlying ontology. The solipsist could for example take quarks and magnetic fields not as part of a physical world (which the solipsist in this sense believes doesn't exist), but as part of his or her own mind.

The explanatory power of such a theory would be strictly identical to that of science, but only for the solipsist, not of course for other people, who by definition literally know that the solipsist's theory is false. False theories have zero explanatory power.

If solipsism is the theory that one's mind is the only thing that we know, then the belief in this theory makes zero difference in terms of the explanatory power of scientific theories. However, solipsism in this sense does not say that the external world is not real. It says that we can only have beliefs about it, not knowledge. Notice that scientists nowadays only claim that scientific theories have a predictive power, not that they are necessarily true of the real world.