Solipsism

Key takeaways

Solipsism belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Solipsism to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Solipsism from memory before moving on to harder problems.

Reference excerpt

Solipsism ( SOLL-ip-siz-əm; from Latin sōlus 'alone' and ipse 'self') is the philosophical position that only one's own mind is certain to exist. It holds that knowledge of anything outside one's own mind, including the external world and other minds, is uncertain and cannot be conclusively known.

Varieties There are varying degrees of solipsism that parallel the varying degrees of skepticism:

Metaphysical

Metaphysical solipsism is a variety of solipsism based on a philosophy of subjective idealism. Metaphysical solipsists maintain that the self is the only existing reality and that all other realities, including the external world and other persons, are representations of that self, having no independent existence. There are several versions of metaphysical solipsism, such as Caspar Hare's egocentric presentism (or perspectival realism), in which other people are conscious, but their experiences are simply not present.

Epistemological

Epistemological solipsism is the variety of idealism according to which only the directly accessible mental contents of the solipsistic philosopher can be known. The existence of an external world is regarded as an unresolvable question rather than actually false. Further, one cannot also be certain as to what extent the external world exists independently of one's mind. For instance, it may be that a God-like being controls the sensations received by the mind, making it appear as if there is an external world when most of it (excluding the God-like being and oneself) is false. However, the point remains that epistemological solipsists consider this an "unresolvable" question.

Methodological

Methodological solipsism is an agnostic variant of solipsism. It exists in opposition to the strict epistemological requirements for "knowledge" (e.g. the requirement that knowledge must be certain). It still entertains the points that any induction is fallible. Methodological solipsism sometimes goes even further to say that even what we perceive as the brain is actually part of the external world, for it is only through our senses that we can see or feel the mind. Only the existence of thoughts is known. Methodological solipsists do not intend to conclude that the stronger forms of solipsism are actually true. They simply emphasize that justifications of an external world must be founded on indisputable facts about their own consciousness. The methodological solipsist believes that subjective impressions (empiricism) or innate knowledge (rationalism) are the sole possible or proper starting point for philosophical construction. Often methodological solipsism is not held as a belief system, but rather used as a thought experiment to assist skepticism (e.g. René Descartes' Cartesian skepticism).

Main points

Mere denial of material existence, in itself, does not necessarily constitute solipsism. Philosophers generally try to build knowledge on more than an inference or analogy. Well-known frameworks such as Descartes' epistemological enterprise brought to popularity the idea that all certain knowledge may go no further than "I think; therefore I exist." Descartes' view provides one key detail about the nature of the "I" that has been proven to exist, its relation to a God of positive attribution. The theory of solipsism also merits close examination because it relates to three widely held philosophical presuppositions, each itself fundamental and wide-ranging in importance:

One's most certain knowledge is the content of one's own mind—my thoughts, experiences, affects, etc. There is no conceptual or logically necessary link between mental and physical—between, for example, the occurrence of certain conscious experience or mental states and the "possession" and behavioral dispositions of a "body" of a particular kind. The experience of a given person is necessarily private to that person. To expand on the second point, the conceptual problem is that the previous point assumes mind or consciousness (which are attributes) can exist independent of some entity having this attribute (a capability in this case), i.e., that an attribute of an existent can exist apart from the existent itself. If one admits to the existence of an independent entity (e.g., the brain) having that attribute, the door is open to an independent reality. Some philosophers hold that, while it cannot be proven that anything independent of one's mind exists, the point that solipsism makes is irrelevant. This is because, whether the world as we perceive it exists independently or not, we cannot escape this perception, hence it is best to act assuming that the world is independent of our minds.

History Origins of solipsist thought are found in Enlightenment thinkers such as Thomas Hobbes and Descartes.

René Descartes The foundations of solipsism are in turn the foundations of the view that the individual's understanding of any and all psychological concepts (thinking, willing, perceiving, etc.) is accomplished by making an analogy with their own mental states; i.e., by abstraction from inner experience. This view, or some variant of it, has been influential in philosophy since René Descartes elevated the search for incontrovertible certainty to the status of the primary goal of epistemology, whilst also elevating epistemology to "first philosophy".

Berkeley

George Berkeley's arguments against materialism in favour of idealism provide a solipsist with a number of arguments not found in Descartes. While Descartes defends ontological dualism, thus accepting the existence of a material world (res extensa) as well as immaterial minds (res cogitans) and God, Berkeley denies the existence of matter but not minds, of which God is one.

Relation to other ideas

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Solipsism

Start with the simplest possible case. Write down what Solipsism claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Solipsism before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Solipsism ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Solipsism

In research: Solipsism appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Solipsism in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Solipsism is common in secondary-school and first-year university syllabi. It links to neighbouring topics Egoism, Epistemological theories, Idealism, so understanding it makes those chapters shorter.
In everyday life: Look for Solipsism outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Solipsism in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Solipsism means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Solipsism out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Solipsism in simple terms?

Solipsism ( SOLL-ip-siz-əm; from Latin sōlus 'alone' and ipse 'self') is the philosophical position that only one's own mind is certain to exist. It holds that knowledge of anything outside one's own mind, including the external world and other minds, is uncertain and cannot be conclusively known.

Why does Solipsism matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Solipsism?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Solipsism.