Category: consciousness
Type: argument
Associated thinker(s): John Stuart Mill (an influential formulation of the argument from analogy)
Original publication or approximate period: Mill, An Examination of Sir William Hamilton’s Philosophy (1865); earlier antecedents
Difficulty: Beginner
Themes: other minds, analogy, evidence
Related experiments: Philosophical Zombies; What Is It Like to Be a Bat?; Beetle in a Box; Inverted Spectrum
You are directly aware of your own thoughts and feelings, but the thoughts and feelings of others are not available to you in the same way. When a friend winces after stubbing a toe, you take her to feel pain. What entitles you to that conclusion?
A classical reply is an argument from analogy. In Mill’s formulation, I know in my own case that bodily conditions and outward signs are connected with feelings; when others have similar bodies and display similar signs, this supports an inference that they have similar feelings. The SEP entry presents Mill’s statement as an influential formulation, not the first version of the idea.
How can anyone know that other beings have minds, and what could count as evidence for it?
On the traditional epistemological framing, belief in other minds raises a question about evidence that ordinary social life rarely makes explicit. Questions about how we understand minds also arise in work on infants and non-human animals. This article’s extensions to people who cannot communicate and to artificial systems are teaching applications, not claims that the SEP entry settles those cases.
The analogy argument has been criticized for relying on one’s own case, but defenders dispute that this is a decisive weakness: they point to repeated correlations between mental states and behavior, or defend the relevance of similarities in bodily causes. The force of the argument therefore depends on which version and defense are being considered.
The argument from analogy uses similarities between one’s own case and other people’s bodies and behavior as support for inferring similar mental states. Critics question whether the inference can be checked and whether it generalizes from one case; defenders offer different replies, so the objection is not a settled refutation.
Inference to the best explanation treats other people’s mental states as an explanation of their behavior. The SEP describes this as a prominent alternative, while also recording objections to treating it as a complete account.
Criteria-based and Wittgensteinian approaches challenge the picture of mental states as private inner objects that we first identify in ourselves and then infer in others. They ask how mental concepts are learned and applied, and how behavior can function as a criterion for applying them. Philosophers disagree about what this approach establishes and whether it removes the epistemological problem.
Perceptual accounts argue that in at least some cases—such as seeing pain in a person’s expression—we can perceive another’s state rather than infer it from behavior. The view is contested, and its proponents do not claim that every mental state is directly perceptible or that such perception is infallible.
Testimony-based accounts treat what another person says as a possible basic source of knowledge about their mental states. These approaches address the source of our knowledge differently; none is presented here as settling every version of the problem.
A question about whether, or how, we know that others have minds is not the same as a claim that they do not have minds. Radical skeptical scenarios—including the possibility that others are mindless despite behaving like us—pose a philosophical challenge; they do not by themselves establish solipsism. The SEP distinguishes epistemological questions about knowledge from conceptual questions about how we think and speak about minds, and notes that these may also connect with metaphysical questions about what minds are.
This problem should also not be confused with the hard problem of consciousness, which asks why physical processes give rise to experience at all.
Comparing humans with animals or unfamiliar beings tests how much an analogy depends on shared bodies and behavior; other approaches may appeal to explanation, perception, or testimony instead. Extending the question to machines is a teaching prompt, not a historical variation attributed to Mill or a conclusion established by the sources. A case in which a human shows no familiar behavioral signs of consciousness is another teaching prompt about the limits of behavioral evidence.
The SEP entry was consulted in its sections on the epistemological problem, the argument from analogy, best explanation, criteria, perceptual knowledge, and the history from Descartes to Mill. It quotes Mill’s formulation and cites the 1865 work; this review did not verify that passage against a complete reading of Mill’s primary text. The historical note therefore identifies Mill as an influential formulation, not the originator of the argument. The examples and extensions identified above as teaching prompts are editorial framing.
Research check: 2026-11-01. This is an educational explanation, not a substitute for the primary texts or an exhaustive account of the debate.