What Refutation of Solipsism Teach About Philosophy of Science

Abstract:

Solipsism, a philosophical position dating back centuries, holds that only one’s mind is certain to exist. This idea challenges conventional notions of reality and the external world, raising profound questions about the nature of existence, knowledge, and perception. This essay delves into the historical roots of solipsism, examines key arguments for and against the theory, and explores its implications for understanding consciousness and reality. Contrary to embracing solipsism as a tenable philosophical position, I argue that it functions best as a provocative thought experiment designed to expose the absurdities inherent in its extreme skepticism, begging refutation. Moreover, I contend that the refutations of solipsism, such as Russel’s and Wittgenstein’s, offer valuable insights for the philosophy of science and enrich discussions within the science versus religion debate.

Introduction:

Solipsism, derived from the Latin words solus (“alone”) and ipse (“self”), is a philosophical position that holds that the self is the only thing that can be known to exist with certainty. This radical position suggests that the external world, including other minds and physical objects, may be mere products of one’s own consciousness. A solipsist maintains that there is no proof that anything external to one’s own mind actually exists. Solipsism, as an epistemological position, argues that knowledge of anything outside one’s own mind is uncertain, as the external world and other minds cannot be known directly, only through representations constructed by one’s own mind. While solipsism is often dismissed as an extreme skepticism, its implications have fascinated philosophers throughout history and continue to provoke debate and contemplation.

Solipsism, a radical form of skepticism, posits that the only thing one can be certain of is the existence of one’s mind. It casts doubt on the external world, including the existence of other minds and physical objects, suggesting that these may be mere projections of one’s own consciousness. Solipsism challenges traditional epistemological assumptions by questioning the reliability of sensory perception and empirical evidence. While skepticism in philosophy typically involves doubting the possibility of certain knowledge, solipsism takes skepticism to its extreme by questioning even the existence of an external reality independent of the self. Despite its provocative nature, solipsism raises profound questions about the nature of existence, knowledge, and perception, inviting reflection on the limitations of human understanding and the boundaries of reality.

Different varieties of solipsism have been proposed.

Methodological solipsism is the agnostic form of solipsism. While methodological solipsists do not deny outright the existence of an external world, they contend that the external world cannot be directly observed or proven. The only realities we can be certain of are those arising within one’s own mind.  Some methodological solipsists take the position that even one’s own brain is a part of the external world, which reality cannot be known for certain—only one’s thoughts and subjective experiences are certain.

As a methodological principle, solipsism holds that empirical inquiry should focus on subjective impressions and one’s own immediate experiences as the primary foundations for certain knowledge. Speculation about the nature of external reality or other minds is avoided or minimized. Only the reality of one’s consciousness is fully evident and demonstrable.

Methodological solipsists adopt this position not necessarily because they subjectively believe only their own minds exist, but because they argue absolute knowledge concerning an observer-independent world cannot be attained scientifically or philosophically. All anyone can do is study the workings of their own consciousness. The solipsist’s self forms the limits of the knowable domain.

The methodological solipsist perspective, while avoiding outright denial of reality, contends that philosophical and scientific inquiry should concern itself only with subjective experiences, not with reality claims about unobservable entities outside one’s own mind. It is agnostic skepticism about the external world taken to its logical methodological conclusion.

Epistemological solipsism is a stronger form of skepticism, maintaining that no reality exists outside of one’s own mind. While methodological solipsism only makes claims about the limits of knowledge, epistemological solipsism makes the stronger ontological claim that only one’s own conscious mind genuinely exists.

The epistemological solipsist argues that the external world, physical objects, and other minds have no reality independent of one’s own perceptions and conceptions. Since we cannot directly observe anything beyond our own mental states, there is no reason to posit anything else as objectively real. There is no evidence that other entities exist apart from our subjective representations of them within our consciousness.

Proponents of epistemological solipsism contend that believing in the existence of an external world requires making unjustifiable assumptions. They assert that the only things that can be known to exist for certain are the contents of one’s own mind—sensations, thoughts, emotions, imaginations, etc. We have no way to prove physical objects persist unperceived, so we cannot be compelled to grant them truly independent existence.

In this radical form of skepticism, knowledge of reality is limited to self-knowledge—even one’s own body exists only as a phenomenon within consciousness. The self-contained mind constitutes the whole of reality, and imagining a realm beyond it is mere speculation devoid of any epistemic warrant. Epistemological solipsism thereby rules out knowledge of any reality beyond one’s own mental states.

Metaphysical solipsism is the philosophical stance that only one’s own mind exists, constituting the whole of reality. It goes beyond skepticism about the external world by outright denying any reality beyond one’s own mental states.

Under metaphysical solipsism, there are no physical objects, other minds, or observable phenomena independent of one’s own perceptions and conceptions. Everything aside from one’s solitary consciousness is deemed to be non-existent. The self-contained mental sphere of sensations, thoughts, and experiences comprises the totality of being.

Metaphysical solipsists do not merely doubt the ability to know or prove the existence of anything beyond their own minds, as with epistemological solipsism. Rather, they posit that no such external reality exists at all. There are no unattained or unobserved objects or events. All arise from and subsist within the generating mind.

By restricting existence to subjective mental phenomena alone, metaphysical solipsism takes the extreme position that reality is coextensive with individual consciousness. It rules out any assumption of a wider world, regarding such as not just unknowable, but fictional. Only the solipsistic mind remains real when taken to this absolute ontological extreme.

Historical Background:

The roots of solipsism can be traced back to ancient philosophical traditions. Greek philosophers such as Protagoras famously declared that “man is the measure of all things” (Protagoras), emphasizing the subjective nature of perception and knowledge. Similarly, in Hindu philosophy, for example, the concept of atman (“self”) suggests that the individual soul is identical to the ultimate reality, Brahman (Chandogya Upanishad, Brihadaranyaka Upanishad, and Katha Upanishad).

In Continental philosophy, George Berkeley stands out as a philosopher who, perhaps, came closest to solipsism. Berkeley’s philosophical system, known as subjective idealism, posits that the only things that truly exist are minds and their ideas. He famously argued, esse est percipi (“to be is to be perceived”) (Berkeley, 1713 [1992]), suggesting that the existence of objects depends on their being perceived by a mind. In other words, according to Berkeley, the external world is fundamentally dependent on perception, and nothing exists independently of the mind.

While Berkeley’s philosophy shares some similarities with solipsism, particularly in its emphasis on the primacy of the mind and perception, Berkeley did not deny the existence of other minds. Instead, he believed that all minds, including our own, are ultimately perceptions in the mind of God. Thus, Berkeley’s idealism differs from traditional solipsism in important respects.

Emmanuel Kant also doubted the ability to know the true nature of objects: “Things which we see are not by themselves what we see. It remains completely unknown to us what the objects may be by themselves and apart from the receptivity of our senses. We know nothing but our manner we perceive them” (1781 [1929]). Kant was not a solipsist, but, according to Kant, we can only be certain of the representation of the objects in the subject.

Key Arguments for Solipsism:

One of the central arguments for solipsism is the problem of other minds. Since one can only directly access one’s own thoughts and experiences, it is impossible to verify the existence of other minds with certainty. Descartes famously remarked, cogito ergo sum (“I think, therefore I am”) (1637), highlighting the self-evident nature of one’s own consciousness while casting doubt on the existence of external realities. (1641)

Descartes sought to find a foundation for knowledge that was absolutely certain (1641) He did this by systematically doubting all of his beliefs until he arrived at something indubitable. He hypothesized the existence of an “evil demon” who has denied us access to reality and instead feeds us sensory input that is completely fabricated. 

Descartes considered whether we can actually trust our senses to deliver true beliefs about the external world, given the possibility that an evil demon is manipulating our perceptions. Arguendo, if such a demon exists, then it could make us believe wholeheartedly that the external world around us is real when in fact none of it actually exists outside of our minds.

This radical skepticism leads to the realization that the only thing we can be absolutely certain of is the existence of our own minds and consciousness. After all, in order to be deceived, one must exist in the first place. The cogito remains valid even if our perceptions are completely fabricated by an evil demon. At the very least, our minds carrying out the doubting and deception must be real.

Thus, the evil demon gedanken (“thought”) experiment reveals the limits of our knowledge when relying purely on sensory perception, and prompts Descartes to find metaphysical certainties that cannot be doubted or manipulated, beginning with the existence of the thinking self. This laid the groundwork for his rationalist epistemology and cogito ergo sum realization.

Another argument for solipsism stems from the indistinguishability of dreams and waking life. In dreams, one can experience vivid and immersive visions that seem indistinguishable from reality. This raises the question: if reality is subjective and constructed by the mind, how can one differentiate between waking life and the dream world?

This argument was eloquently expressed by Daoist Chinese philosopher Zhuangzi (or Zhuang Zhou, c. 4th century BCE), who describes a dream in which he experienced being a butterfly, and upon waking, he reflects on whether he is Zhuangzi who dreamed that he was a butterfly or a butterfly who dreams that it is Zhuangzi^[1] (1968). This contemplation of the nature of reality and the self blurs the distinction between dreams and waking life—one of the main arguments for solipsism.

Rebuttals and Criticisms:

Critics of solipsism have raised various objections to the theory. One common critique is the problem of solipsistic isolation. If one truly believes they are the only conscious being, it leads to a profound sense of loneliness and disconnect from the external world. Additionally, solipsism undermines the possibility of meaningful communication and interpersonal relationships, as other individuals are reduced to mere projections of one’s own mind. Note, however, that these objections are not logical proofs of the fallacy of solipsism, but merely critiques based on the negative psychological and sociological implications of this philosophical worldview for a person who espouses it as well as for society.

Philosophers such as Bertrand Russell have also argued against solipsism by appealing to empirical evidence and scientific reasoning. The consistency and predictability of the external world, as well as the success of scientific inquiry, suggest that there is an objective reality independent of individual perception (Russell, The Problems of Philosophy, 1912). Russell also rejects solipsism on the basis of its contradiction of our intuitive understanding of the external world and the existence of other minds. He argues that while solipsism may seem logically possible, it goes against our deeply ingrained convictions about the reality of the external world and the existence of other people.

Wittgenstein (1921), in his Tractatus Logico-Philosophicus, touches upon language and its limitations in conveying solipsistic ideas, contributing to the broader philosophical discourse on the topic.

In his later philosophical work, Ludwig Wittgenstein argued against the need for absolute certainty in knowledge assumed by solipsism^[2] (1972). His idea of “hinge certainty” posits that there are basic foundational beliefs underpinning knowledge that cannot themselves be proven with absolute logical certainty.^[3]

For example, the belief that the external world exists cannot be proven with deductive logic, but it underlies so much of our knowledge that to doubt it would unravel all empirical knowledge. Wittgenstein argued these “hinge certainties” are not themselves subject to doubt because they are the foundation on which knowledge depends.

Wittgenstein’s perspective contends that the solipsist demand for absolute certainty about the external world is misguided. Knowledge need not require ironclad logical proof, but relies on basic frameworks of belief that cannot themselves be proven but are relied upon to make sense of experience and information.

In this way, Wittgenstein provides grounds for rejecting the rigid assumptions of solipsism about knowledge and certainty. His idea of hinge certainty shows solipsism’s requirements are incoherent and argues that knowledge can exist without disproving solipsism, bypassing its demand for logically incorrigible truths. Wittgenstein’s philosophy demonstrates flaws in the premises underlying solipsist epistemology.

Chisholm (1942) addresses the problem of the criterion, challenging solipsism’s implications for knowledge and justification, particularly concerning how one can determine whether a belief is justified or knowledge is attainable without already presupposing some standard or criterion for justification. Chisholm argues that any attempt to establish such a criterion would ultimately rely on circular reasoning or infinite regress, as any criterion must itself be justified by some further criterion. This dilemma poses a significant challenge to foundationalist and coherentist theories of epistemic justification, including solipsism.

Wittgenstein—Gödel—Heisenberg Parallel

The philosophical connection between Wittgenstein’s critique of solipsism, Gödel’s incompleteness theorems, and Heisenberg Uncertainty Principle is clear: Wittgenstein, Gödel, and Heisenberg contend that absolutely certain, complete knowledge is an unrealistic ideal. They demonstrate limits on systematic, formal reasoning about truth and limitations on empirical knowledge.

A number of authors have drawn a parallel between the views of Wittgenstein and Gödel. In his book “Pi in the Sky: Counting, Thinking, and Being” (1992), philosopher John D. Barrow compared the views of Wittgenstein and Gödel, noting that both showed definitive limits to mathematical logic and formal systems of reasoning. Logician George Boolos also linked Wittgenstein’s ideas in “On Certainty” to Gödel’s theorems (Boolos, 1993). He argued both demonstrated the impossibility of an ideal formal system. Philosopher Marjorie Perloff devoted a chapter to connecting Wittgenstein and Gödel in her 1999 book “Wittgenstein’s Ladder: Poetic Language and the Strangeness of the Ordinary.” She highlighted their shared conception of incompleteness in logical systems trying to fully encapsulate truth. Allan Janik and Stephen Toulmin analyze parallels between Wittgenstein and Gödel’s perspectives on certainty and completeness as revealing limitations of formal systems (1973).

Indeed, Wittgenstein argues that the solipsist demand for logically certain knowledge about reality is misguided. There are always some foundational “hinge certainties” relied upon in reasoning that cannot themselves be proven. As Wittgenstein puts it: “The game of doubting itself presupposes certainty” (1969).

Similarly, Gödel’s incompleteness theorems prove that no sufficiently complex logical or mathematical system can be both consistent and complete. There will always be true statements within the system that cannot be formally proven true or false within the system itself. Formal reasoning has intrinsic limitations.

Heisenberg’s uncertainty principle (formulated in 1927) states that there are intrinsic limits to how precisely we can know complementary properties of quantum particles like position and momentum. There is an unavoidable uncertainty in measuring quantum systems.

Wittgenstein critiques the assumptions behind solipsism’s radical skepticism, showing it relies on impossible standards of proof. Gödel formally proves that logical systems cannot completely explain all truth within them. Absolute certainty is impossible. And Heisenberg proved the perfect empirical knowledge is unattainable. As he wrote: “We cannot know, as a matter of principle, the present in all its details” (1958).

An interesting parallel can be found in comparing Heisenberg’s Uncertainty Principle with Gödel’s incompleteness theorem. Heisenberg showed that in quantum mechanics, perfect knowledge of complementary variables, such as the position and momentum of a subatomic particle, is impossible—we can’t know both with arbitrary precision. Gödel proved that sufficiently complex mathematical systems cannot be both complete and consistent—there will always be true statements that cannot be formally proven within the system. Heisenberg revealed an unavoidable indeterminacy in physics. Gödel showed that even in mathematics, there are indeterminate propositions, whose truth cannot be definitively proven or disproven.

The parallel between Heisenberg’s uncertainty principle and Gödel’s incompleteness theorems has been noted and analyzed by a number of authors. Physicist and philosopher Brigitte Falkenburg draws parallels between them, noting they both demonstrate limits to formal systems (2006). Douglas Hofstadter devotes a chapter to comparing them in his book “Gödel, Escher, Bach,” highlighting their profound implications (1979). Philosopher Rebecca Goldstein joins both ideas together, using heuristic devices like Heisenberg’s microscope thought experiment (2005). Physicist David Lindley explores parallels between Heisenberg and Gödel (2007). Cristian Soto analyzed the conceptual connections between the two results and their philosophical significance (Soto, 2021).

Both Wittgenstein and Gödel undermine the classical notion of attaining certainty through step-by-step deductive reasoning alone. Whether in philosophy or formal logic, there are always unfounded assumptions relied upon in constructing systems of knowledge. The demand for completeness and absolute proof is untenable. Although Heisenberg’s Principle is not related to formal deductive reasoning, it shows a remarkable parallel between formal logic and philosophy on the one hand and nature on the other hand.

Wittgenstein offers a conceptual critique of solipsism, while Gödel provides a formal mathematical proof of the incompleteness theorem. But both demonstrate that any system of knowledge rests on basic, uncertain foundations. Heisenberg extends this notion to the empirical domain, which is constrained by his Uncertainty Principle. Certainty remains elusive. Thus, they provide complementary perspectives on the inherent limits of systematic knowledge, formal reasoning about truth, and empirical data. Rather than attainable certainties, Wittgenstein, Gödel, and Heisenberg point to endemic uncertainties underlying our understanding of the world. The quest for absolute objective knowledge through reason and science has limits.

Implications and Conclusions

Solipsism presents us with a conundrum—it is absurd prima facia, and yet it is impossible to refute logically; it is repulsive in its narcissistic self-centeredness and, at the same time, elegant in its simplicity, consistency, and explanatory power.

Historically, there was hardly a serious philosopher who could be truly called a solipsist. I don’t know any philosopher today who believes solipsism is a viable philosophical position that could be adopted as one’s weltanschauung. One has to be insane to believe that one’s mind is the only thing that really exists—such a view would justifiably be considered a psychiatric pathology.

In my view, solipsism was never meant to be a philosophy to embrace as one’s own. Instead, it was meant to be an extremely elegant and powerful gedanken experiment with much to teach us. Indeed, the Cartesian “evil demon” was a classic gedanken experiment. Solipsism begs to be refuted. And its various refutations hold powerful lessons for science, philosophy, and the philosophy of science.

Bertrand Russell thought solipsism could be refuted based on empiricism and human intuition. First, solipsism contradicts our empirical experience and underminds the entire scientific enterprise as futile. Second, Russell rejects solipsism on the basis of its contradiction of our intuitive understanding of the external world and the existence of other minds. Russell’s critique of solipsism highlights the importance of intuition and common sense in philosophical inquiry.

This lesson comes to mind whenever some philosophers or physicists pontificate that time is not real but a psychological illusion. I can think of nothing else more counterintuitive and irritating. Like solipsism, such assertions violate our deepest intuition and empirical experience. Time is a fundamental aspect of human perception and experience, integral to our understanding of events, causality, and change. To deny the reality of time is to reject the framework through which we comprehend the passage of events and the ontological unfolding of reality. Just as solipsism challenges the existence of an external world beyond our own consciousness, confining time to our minds as an illusion undermines the foundation of our understanding of temporal existence and the continuity of experience. While it may be tempting to entertain abstract notions of timelessness or the illusion of temporal progression, such extravagant ideas run counter to the lived experiences of individuals and the collective observations of humanity throughout history. In essence, denying the reality of time, like solipsism, divorces us from the shared reality we perceive and the empirical evidence upon which our understanding of the world is built, leading to a philosophical position that is isolated and disconnected from common human experience. Thinking about solipsism may be a helpful remedy to those thinkers who succumb to this fallacy.

The same can be said about the deniers of free will. Much ink has been spilled debating this counterintuitive view. Denying the reality of free will, akin to solipsism, challenges our intuitive understanding of agency and conflicts with our empirical experience of decision-making and autonomy. Free will is a cornerstone of human experience, shaping our sense of responsibility, choice, and moral accountability. To deny the reality of free will is to reject the notion that individuals possess the capacity to make genuine choices and act independently of deterministic forces. Just as solipsism undermines our belief in the existence of an external world beyond our own consciousness, denying free will erodes the foundation of our understanding of personal autonomy and moral agency. While it may be tempting to adopt deterministic or compatibilist views that suggest our actions are predetermined or constrained by external factors, such ideas run counter to the deeply ingrained sense of freedom and volition that characterizes human experience. In essence, denying the reality of free will, like solipsism, undermines our connection to the lived reality we perceive and the empirical evidence of human choice and agency, leading to a philosophical position that is disconnected from the intuitive understanding of personal responsibility and moral decision-making.

Last, I want to touch on the science vs religion debate in view of the lessons taught by solipsism.

Bertrand Russell advocated the superiority of reason and science over religious faith. In his 1927 lecture “Why I Am Not A Christian,” Russell argues that “what science cannot tell us, mankind cannot know” and that rational inquiry is the sole path to knowledge (1957). This is a fairly typical attitude, particularly in scientific circles.^[4] However, as Wittgenstein and others have pointed out, if we rely solely on reason, solipsism is logically irrefutable, potentially undermining scientific realism. Accepting the existence of an external world requires a foundational faith that cannot be proven through reason alone. On this perspective, science proceeds on basic assumptions about reality that must be taken on faith. Thus, complete certainty through reason may be unattainable, and an act of faith is required to allow for empirical inquiry. This realization, which we owe to the gedanken experiment of solipsism, injects a healthy dose of humility into debates about the status of religious faith versus scientific knowledge, as both are built on unprovable beliefs about the nature of reality. Absolute positions of scientific superiority fail to recognize these shared uncertainties at the foundations of human knowledge.

Viewed as a gedanken experiment leading to a prima facia absurd position, solipsism beckons for refutation, offering insights that extend beyond the confines of metaphysical discourse. Its implications resonate with the philosophy of science and the ongoing discourse surrounding the science versus religion debate. Russel’s refutation of solipsism underscores the significance of valuing common sense and intuition when confronting extravagant philosophical ideas. Wittgenstein’s approach to the refutation of solipsism offers common ground for the discussions regarding religious faith versus scientific reason, as both rely on foundational beliefs and a leap of faith. Attempts to refute solipsism illuminate the shared uncertainties inherent in various knowledge systems. Thus, when viewing solipsism as a provocative thought experiment, absurd by design and begging refutation, engaging philosophically with this concept can enrich our understanding of the limits of knowledge and the intricate relationships between faith, reason, and belief across diverse realms of intellectual inquiry.

References

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Chandogya Upanishad, Brihadaranyaka Upanishad, and Katha Upanishad. (n.d.). In Upanishads.

Chisholm, R. (1942). The Problem of the Criterion. Journal of Philosophy.

Coyne, J. A. (2015). Faith versus Fact: Why Science and Religion Are Incompatible. Penguin.

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Endnotes:

[1] Zhuangzi writes, “Once Zhuangzi dreamt he was a butterfly, a butterfly flitting and fluttering around, happy with himself and doing as he pleased. He didn’t know he was Zhuangzi. Suddenly he woke up and there he was, solid and unmistakable Zhuangzi. But he didn’t know if he was Zhuangzi who had dreamt he was a butterfly, or a butterfly dreaming he was Zhuangzi. Between Zhuangzi and a butterfly, there must be some distinction!”

[2] Wittgenstein’s book On Certainty was written in the last 18 months of his life between 1949-1951 and posthumously published. See propositions 1, 4, and 12.

[3] Witgenstein’s “hinge certainties” are the foundations of knowledge. Specifically, hinge certainties refer to fundamental beliefs or assumptions that underpin our knowledge but cannot themselves be proven. Wittgenstein argued that some basic certainties, like our belief in the existence of the external world, cannot be reduced to deductive logic or empirical proof. However, these certainties function as a framework upon which all our empirical knowledge and beliefs hang. They are “hinges” on which knowledge “turns.” Wittgenstein used the metaphor of a hinge (something that itself stays fixed but allows movement) to characterize these basic certainties underlying knowledge. Hinge certainties are not themselves subject to doubt—they are the unquestioned grounds that make doubt and knowledge possible in the first place. Examples include belief in the independence of physical objects, the reliability of memory, the law of causality, the passage of time, etc. These certainties cannot be proven true, but doubting them would undermine all empirical knowledge and reasoning. Therefore, hinge certainties rely on communal practices and ways of acting, not on formal logic or proof. They are the unfounded grounds of real inquiry. This Wittgensteinian perspective counters philosophical skepticism’s demand for absolute logical certainty about everything. Hinge certainties show that not all knowledge requires indubitable justification.

[4] Just to give one more recent example, Biologist Jerry Coyne contends science and faith are “fundamentally incompatible” as methods of inquiry. He argues that science relies on reason, evidence, and skepticism, while religion relies on faith, revelation, and dogma (Coyne, 2015).