SOLVING THE SCEPTICAL PROBLEM CONCERNING THE EXTERNAL REALITY ###

This is the draft of a paper to be published. It develops the ideas already presented in the paper called "The Sceptical Deal with the Concept of Reality", published in the book called LINES OF THOUGHT (CSP 2014) 

 

Two Concepts of Reality and the Dissolution of Scepticism

 

 

Summary:

This paper argues that external world scepticism arises from an unnoticed ambiguity in the notion of reality. Once we distinguish inherent reality – the status of experience as genuine from within a world – from adherent reality – the status a world has relative to other possible worlds – the sceptical demand for demonstrative proof is revealed as conceptually misguided. Inherent reality is demonstrable, since it is given in the structural features of experience and extends, via causal integration, to both directly and indirectly accessible entities. Adherent reality, by contrast, is not demonstrable, because establishing it would require comparative access to multiple worlds, a standpoint our epistemic situation rules out. The classical sceptical dialectic collapses because it presupposes a univocal notion of reality and attempts to meet an incoherent demand. What remains is the Realist Presupposition (RP): in the absence of evidence for a sceptical scenario, we are entitled to assume that the external world is both inherently and adherently real. RP is not a metaphysical thesis but a rational orientation grounded in explanatory economy and the conditions under which doubt is intelligible.

Keywords: reality; dissolution of scepticism; rational presupposition; external world scepticism; explanatory economy; hinge epistemology; conceptual analysis.

 

The problem of external‑world scepticism has long been regarded as one of the deepest and most persistent challenges in epistemology. Its force derives from a simple but powerful thought: our experience is compatible with radically different underlying realities, and nothing within experience itself seems capable of ruling out these alternatives. From this, the sceptic concludes that we cannot know that the external world is real (Descartes 1641, Meditation I). By contrast, the classical anti‑sceptical tradition (Reid 1764; 1785) maintains that we do know this and that sceptical alternatives are not genuine epistemic possibilities but artefacts of a mistaken theory of perception. Despite centuries of reformulations, refinements, and attempted dissolutions, the dialectic continues to exert pressure on our epistemological self‑understanding.

   This paper argues that the dialectic persists only because it rests on a conceptual mistake. The sceptical problem arises from a confusion in the underlying concept of reality. It depends on an unnoticed ambiguity: sceptical arguments presuppose that the attribution of reality constitutes a single epistemic status that the world either possesses or fails to possess, and anti‑sceptical responses typically accept this assumption while disputing the sceptic’s conclusion. I argue that this presupposition is false. The notion of reality is not univocal. It divides into two fundamentally different concepts – inherent reality and adherent reality – each with its own epistemic profile, criteria, and conditions of assessment. Once this distinction is made explicit, the sceptical problem is transformed. The sceptic’s demand for demonstrative proof is revealed as conceptually misguided, and the familiar anti‑sceptical responses are shown to inherit the same mistake. In this way, the entire dialectic collapses.

   The argument of this paper is not a variation on familiar anti‑sceptical strategies. It does not rely on denying closure principles (Dretske 1970; Nozick 1981), on contextualist manoeuvres (DeRose 1995; Williams 1996; Zhao 2026), on disjunctivist accounts of perceptual knowledge (McDowell 1994), on externalist theories of warrant (Britt 2026), on modal dissolutions of sceptical reasoning (Bangu 2018), or on transcendental arguments (Strawson 1959). Nor does it attempt to defeat scepticism by claiming that sceptical hypotheses are probabilistically negligible (Vogel 1987), explanatorily inferior (Lycan 2001), semantically incoherent (Putnam 1981), or pragmatically irrelevant to our epistemic practices (Stroud 1984). The approach developed here is of a different kind.

   Instead, it proceeds by conceptual analysis. It shows that the sceptical problem arises only because we have failed to distinguish two fundamental senses of reality that play different roles in our epistemic lives. Once the distinction is in place, the sceptical demand for demonstrative certainty is exposed as a demand for something that cannot be provided – not because our epistemic powers are limited, but because the demand itself is conceptually incoherent.

   The distinction between inherent and adherent reality reflects a structural feature of our epistemic situation. Inherent reality concerns the status of experience within a world. It is marked by vividness, involuntariness, intersubjective checkability, law‑governed regularity, and contextual coherence. These features converge so strongly that the attribution of inherent reality is forced upon us by the very conditions of intelligible experience. Their scope extends beyond direct perception: through causal integration, they apply equally to indirectly accessible entities such as remote nebulae, bacteria, molecules, and subatomic particles. Properly understood, these criteria yield a straightforward proof of the external world; a result that stands in contrast with Carnap’s defeasible view that the existence of the external world (the “thing world”) is a pragmatic fiat (1950: §2).[1] Inherent reality is demonstrable because it is given in the structure of experience itself.

   Adherent reality, by contrast, concerns the status of a world relative to other possible worlds. It is a comparative notion: a world is adherently real when it stands in the appropriate relation to other worlds that might exist. But adherent reality cannot be demonstrated because demonstration would require access to at least one additional world with which ours could be compared. Such access is conceptually impossible, except in hypothetical sceptical scenarios whose very possibility remains indemonstrable.

   This conceptual point has profound epistemological consequences. It shows that the sceptical demand for proof of external reality in the adherent sense is not merely unmet; it is misconceived. The sceptic asks for a kind of proof that the concept of adherent reality itself excludes. The anti‑sceptic, in attempting to meet this demand, inherits the same mistake. Both sides of the traditional dialectic assume that reality has a single epistemic status. Both sides fail for the same reason.

   Once the conceptual confusion is removed, we can articulate the rational stance that remains. Call it the Realist Presupposition (RP):

RP: In the absence of any evidence for a sceptical scenario, we are rationally entitled to assume that the external world is both inherently and adherently real.

RP is not a metaphysical thesis. It is not a claim about the ultimate nature of reality. It is a rational orientation forced by the structure of our epistemic situation. It replaces the misguided demand for demonstrative proof with a stance that is neither dogmatic nor inferential. It is grounded in explanatory economy (Russell 1912: 26–27) and in the hinge‑epistemological insight that doubt requires evidential motivation (Wittgenstein 1969). RP dissolves the sceptical problem rather than refuting it.

   The structure of the paper is as follows. Section I articulates the distinction between inherent and adherent reality and shows how it reorganises the sceptical dialectic. Section II demonstrates the collapse of the classical sceptical and anti‑sceptical arguments once the distinction is in place. Section III clarifies the Realist Presupposition. Section IV vindicates the Realist Presupposition. Section V concludes by drawing out the broader implications of the view.

   The resulting picture is architectonic. It reorganises the epistemological landscape rather than merely adjusting its contours. It shows that scepticism is not a deep epistemic threat but a product of (deep) conceptual confusion. Once the confusion is removed, the problem disappears.

 

I. Two Concepts of Reality

The sceptical problem arises only because we treat reality as having a single epistemic status. This assumption is so deeply entrenched in philosophical discourse that it is rarely questioned.[2] Yet once we examine the role the concept plays in our epistemic practices, it becomes clear that reality is not univocal. It divides into two fundamentally different notions – inherent reality and adherent reality – each with its own criteria, epistemic profile, and conceptual function. The failure to distinguish these notions is the true source of the sceptical problem.

   This section articulates the distinction and shows how it reorganizes the epistemological landscape. The distinction is not merely terminological. It reflects a structural feature of our epistemic situation. It is the conceptual key that unlocks the sceptical dialectic.

1. Inherent Reality

We begin with the notion of inherent reality. This is the sense of reality operative from within a world; it concerns the status of experience as genuine rather than illusory. Inherent reality is marked by a cluster of features that jointly articulate the ordinary conception of “the real world.” These features may be called criteria of reality, and they are constitutive of what we ordinarily mean by external reality.[3] The fundamental list is the following:[4]

1.     Vividness: perceptual experiences present themselves with maximal intensity and richness, typically sufficient to distinguish them from imagination or hallucination.

2.     Involuntariness: the world imposes itself upon us; its deliverances are not under our control.

3.     Intersubjective checkability: distinct subjects can poaaibly verify the same states of affairs.

4.     Law‑governed regularity: the world exhibits stable patterns that support prediction, explanation, and scientific inquiry.

5.     Contextual coherence: external reality displays synchronic and diachronic coherence with our life histories and expectations; objects stand in recognisable relations to one another, and their temporal trajectories are stable enough to sustain intelligibility, continuity, and foreseeability.[5]

These criteria need not be continuously manifest in every moment of experience. A subject may temporarily lack one or more of them while still living among inherently real things. A drunken or half‑comatose person may fail to enjoy vivid experiences of the objects before him; a castaway may live for years without any possibility of intersubjective verification; someone abruptly transported into an utterly unfamiliar environment may momentarily lack contextual coherence. These absences, however, are local and contingent. They occur against a broader experiential background in which the criteria are jointly satisfiable and, in ordinary circumstances, jointly satisfied. Their occasional suspension does not undermine inherent reality; they presuppose it. Such lapses are intelligible only within a world whose general structure allows the criteria to converge, reinforce one another, and persist across time.

   Crucially, the criteria of reality are not independent. They must be jointly satisfied. They form a mutually reinforcing pattern that persists across time, even across the entire span of a human life. Their convergence is so robust that the attribution of inherent reality is not optional; it is forced upon us by the very conditions of intelligible experience. To deny inherent reality would require rejecting the structural features that make experience possible.

   The necessity of treating the criteria jointly becomes clear once we observe that each can be satisfied in isolation without warranting any attribution of reality.[6]  Consider vividness: subjects suffering from alcoholic hallucinosis may experience hallucinations whose sensory force and clarity are indistinguishable from ordinary perception. Intersubjective checkability can likewise be mimicked: a dream may present itself as shared with other agents, each apparently confirming the same events. Law‑governed regularity and contextual coherence admit similar counterexamples: one may have a monotonously orderly dream in which nothing violates familiar constraints of nature, or a dream that unfolds with perfect contextual continuity.

   These cases show that the satisfaction of any single criterion, or even several in combination, does not compel the attribution of reality. What is impossible, however, is the convergence of all five criteria in a way that yields a stable and intelligible experiential structure. The point is not that such convergence must persist for an entire lifetime. Rather, what matters is that the criteria come together with sufficient stability, depth, and explanatory coherence to form a unified pattern. Once the world supplies an integrated account of the subject’s experiences – one in which vividness, involuntariness, intersubjective checkability, regularity, and contextual coherence mutually reinforce one another – the attribution of inherent reality becomes unavoidable. In such circumstances, we are entitled, indeed forced, to say: it is real; it was real: inherently real.

   The criteria of inherent reality supply a reliable demonstration of the existence of the external world, precisely what Kant lamented as the “scandal of philosophy” in its absence. These criteria apply first to the things around us: objects, properties, states of affairs, events, and processes. But their scope is not confined to what is directly perceptible. We also apply them, indirectly, to entities accessible only through instrumentation: remote nebulae, bacteria, molecules, subatomic particles, and the forces of nature. Modern telescopes allow us to detect primordial cosmic phenomena that would otherwise remain inaccessible to observation. The trajectories of electrons, protons, muons, and positrons, for example, become visible in a cloud chamber through the condensation of supersaturated vapor. Such extensions are justified because these entities are causally connected to observable phenomena. If A causes B, and B invariably exhibits property R, it is reasonable to extend R to A, mutatis mutandis.

   A more decisive argument for this extension lies in the arbitrariness of the human sensory range. To restrict reality to what human beings can perceive would be mere anthropological chauvinism. Some animals see ultraviolet; others see infrared. Migratory birds “see” magnetic fields. Bats and dogs perceive ultrasound; blue whales detect infrasound that travels across oceans. It is easy to imagine beings whose sensory modalities allow them to perceive bacteria, molecules, or atoms directly—something we ourselves do, to some extent, through olfaction. There is therefore no principled reason to confine inherent reality to direct perception. Scientific realism is simply the recognition of this fact.

   By the way, once we attend solely to the criteria of inherent external reality and understand that they may be satisfied either directly or indirectly, we can even construct a straightforward proof of the external world:

1.     The things presently experienced around us satisfy the criteria of inherent external reality.

2.     Many things experienced in the past satisfied these criteria and satisfied them again when re‑experienced.

3.     (Inductively from 1 and 2) Many things experienced in the past, though not presently experienced, certainly satisfy the criteria of external reality.

4.     We have continually encountered new things that satisfy the criteria of external reality.

5.     (Inductively from 4) There must be many things never experienced that nonetheless satisfy the criteria of external reality.

6.     Testimony is, in general, a reliable means of attaining knowledge.

7.     There is abundant testimony concerning things we have never personally experienced, but that satisfy the criteria of external reality.

8.     (Deductively from 6 and 7) Many things we have not personally experienced are known to be real through testimony.

9.     (From 1, 3, 5, and 8) There is a totality of things: (a) some presently experienced, which satisfy the criteria of external reality; (b) many not presently experienced, but known to satisfy those criteria insofar as they satisfied them in the past; (c) others unknown, but which would satisfy them, given the continual appearance of new things that do satisfy the criteria; (d) many never experienced by us, but known to satisfy the criteria through testimony.

10. “Our external world” is the sum total of things recognized as satisfying the criteria of external reality.

11. (From 9 and 10) Our external world satisfies the criteria of external reality; it exists; it is (inherently) real.

This is why common sense regards the reality of the external world as obvious, and why only a metaphysician, or someone out of his wits, would doubt it. My suggestion is that this line of reasoning has, at some point, been tacitly performed by each of us. Even a cave dweller, if asked whether the world exists, would likely respond with a bored “yes.” Trivial as it may seem, this sort of analysis can be philosophically useful as a critique of metaphysical excess.

   Inherent reality is demonstrable. This point is crucial. Demonstrability here does not mean that inherent reality is established by argument. It means that inherent reality is given in the structure of experience itself. It is not inferred, hypothezised, or assumed; it is recognised. The sceptic cannot coherently deny inherent reality, for the denial would undermine the very conditions under which sceptical reasoning is possible.

   This is the first major result of the distinction: inherent reality is epistemically secure.

 

2. Adherent Reality

The second notion is adherent reality. Whereas inherent reality concerns the status of experience from within a world, adherent reality concerns the status of a world relative to other possible worlds. A world is adherently real when it stands in the appropriate relation to other worlds that exist or might exist—roughly, when it is the “actual” world rather than a simulation, deception, or derivative construct.

   A crucial point must be marked at the outset. Adherent reality cannot be assessed from within a single world. Under ordinary circumstances only one world is accessible to us, and no comparison is possible. The concept becomes operationally meaningful only against the background of a sceptical scenario; only when two inherently real worlds are simultaneously available for comparison. This is not an epistemic limitation but a conceptual feature of the notion itself.

   It is conceivable that the joint satisfaction of the inherent criteria of external reality is not immune to radical sceptical hypotheses. Dreams, Cartesian demons, and brain-in-a-vat scenarios (Brueckner 1986)[7] are at least logically conceivable.[8] Suppose, for instance, that I awake in a strange place, surrounded by unfamiliar beings who nonetheless resemble my newly implanted body. They explain, in fluent English, that I had been a brain in a vat, running the program Philosophy Professor on Planet Earth. This, they tell me, is a standard pedagogical procedure on the planet Omega, designed to cultivate cognitive diversity among its inhabitants. My brain has now been implanted into a healthy Omega body, and I am free to live among them, equipped with the intellectual resources acquired during the Earth‑program.

   Let us further suppose that, after appropriate therapeutic adjustment, I come to inhabit this new world without difficulty. It satisfies all the inherent criteria of external reality: stable objects, coherent causal structure, interpersonal interaction, and the absence of epistemic anomalies. They show me the supercomputers, the vats, the pedagogical apparatus; I meet others who were once brains in vats and who recount their own trajectories. Over time, as I become acquainted with the Omega world and, by experiencing its increasing contextual coherence, I come to regard it not merely as inherently real but also as adherently real. The Earth world, though inherently real, was fictional, its coherence being explained by its origin in the Omega world.

   The choice of which world is adherently real in such a scenario is comparative and explanatory. It is grounded not in the inherent criteria of reality, which are shared by both worlds, but in the greater explanatory coherence of treating one world as the source of the other. The adherently real world is the one that contains the other as its fictional product. In the skeptical scenario, the Earth world is thus explained as a construct generated within the Omega world. Omega is therefore both inherently and adherently real, whereas the Earth world—despite my former conviction—was merely inherently real. Their shared inherency explains why, in the comparison case, we are entitled to call both of them “real”: each satisfies the internal criteria of external reality, even though only one occupies the appropriate explanatory position relative to the other.

   As long as no radical sceptical scenario arises, we assume that both inherent and adherent reality obtain. We apply the Presupposition of Reality (PR) – the assumption, grounded in parsimony and the absence of grounds for doubt, that the world we inhabit is both inherently and adherently real – to the Omega world, and not to the slowly forgotten Earth world. Only upon the discovery of a sceptical scenario are we forced to compare worlds and determine which is adherently real, based on the explanatory superiority of treating the sceptical‑scenario world as the originating one.

   The criteria for the adherent irreality are not stable. Nothing guarantees that the Omega world is the only adherently real world. Perhaps I am being manipulated by the inhabitants of planet Zeta, and Omega is itself fictional. Or perhaps everything is an extraordinarily vivid dream, and I awake again as a philosophy professor on Earth, concluding that Earth is the only inherently and adherently real world. The situation resembles the film The Real Thing, in which characters move from one world to another and then to another. In the final scene, after a shootout in a Western saloon, a tall black man enters and asks: “Could someone tell me whether this is the real world?” The question is intelligible only because multiple inherently real but adherently unreal worlds have been traversed.

   We can even imagine a world in which one lives as a brain in a vat and knows it. Suppose that, for humanistic reasons, Omega punishes irredeemable criminals by condemning them to spend their lives as brains in vats, where they may continue their misdeeds, though somewhat unpleasantly aware that they inhabit an adherently unreal world. The point is not empirical but conceptual: adherent irreality is a comparative explanatory notion, applicable only when two or more inherently real worlds are available for comparison.[9]

   These thought-experiments serve to show that adherent reality is a relational concept which cannot be assessed from within a single world. Defending adherent reality/irreality of a world would require access to at least one additional world with which ours could be compared. Such access exists only in the counterfactual situation in which a sceptical scenario becomes actual. Absent that, our epistemic situation provides no standpoint from which its supposed adherent reality/irreality could be evaluated. We inhabit one world, and only one world is ever accessible.

   This point is not epistemic but conceptual. It is not that we lack evidence or cognitive powers needed to demonstrate adherent reality/irreality. It is that adherent reality is not the kind of thing that can be defended under ordinary circumstances. The concept itself excludes the possibility of demonstration. To demand proof of adherent reality as a relational concept is to ask for something incoherent, not because our epistemic powers are limited, but because the demand violates the concept’s conditions of application.

   This is the second major result of the distinction: as a relational concept, adherent reality is not demonstrable, except in the hypothetical case of a sceptical scenario, where it can be rationally justified.[10]

 

II. Evaluating the Argumentative Structures

Once the distinction between inherent and adherent reality is in place, the familiar sceptical demand for proof is exposed as conceptually misguided. The sceptic asks for a kind of demonstration that the very concept of adherent reality excludes. Under ordinary epistemic conditions, adherent reality is not merely undemonstrable; it is inapplicable, because its assessment requires comparative access to more than one world, and only one world is ever accessible. The anti‑sceptic inherits the same confusion by attempting to provide such proof. The entire dialectic collapses because its central requirement is incoherent.[11]

   This collapse is not a rhetorical manoeuvre. It follows from a deeper point: the sceptical dialectic presupposes that reality names a single epistemic status. Without this presupposition, neither the sceptic’s modus tollens nor the anti‑sceptic’s modus ponens can be convincingly formulated. The distinction between inherent and adherent reality, therefore, does not merely clarify the dialectic; it reorganizes it. It shows that scepticism is not a deep epistemic threat but a product of conceptual confusion. To make this point precise, we must examine the argumentative structures themselves and identify the implicit commitments concerning reality on which they depend.

1. The Sceptic’s Modus Tollens

The familiar sceptical argument is usually presented as:

1.     If we know that the external world is real, then we can rule out sceptical alternatives.

2.     We cannot rule out sceptical alternatives.

3.     Therefore, we do not know that the external world is real.

Its intuitive force derives from a widely accepted epistemic requirement: knowledge demands the ability to exclude relevant alternatives. If we cannot exclude the possibility that we are dreaming, deceived, or simulated, then we cannot know that the external world is real.

   But the argument trades on an unnoticed ambiguity. The sceptic’s conclusion is ambiguous between:

Inherent unreality (our world is dream‑like, illusory, unreal), and

Adherent unreality (our world is not the “real” world relative to other possible worlds).

Ancient scepticism typically aimed at the first conclusion; modern scepticism aims at the second. Once we make explicit the commitments concerning reality that the argument presupposes, the argument aiming at the first conclusion becomes:

1.     If we know that the external world is adherently real, then we can rule out adherently real sceptical alternatives.

2.     We cannot rule out adherently real sceptical alternatives.

3.     Therefore, we do not know that the external world is inherently real.

This version is visibly invalid. It shifts illicitly from adherent reality in the premises to inherent reality in the conclusion. The sceptic’s conclusion does not follow.

   Modern sceptics typically avoid this mistake by aiming only at adherent unreality. Their argument must then be rendered as:

1.     If we know that the external world is adherently real, then we can rule out adherently real sceptical alternatives.

2.     We cannot rule out adherently real sceptical alternatives.

3.     Therefore, we do not know that the external world is adherently real.

This version is deductively valid. And indeed, we cannot prove that our world is adherently real, since adherent reality is not demonstrable. But this does not matter. The sceptic’s conclusion is epistemically idle, since we have good reason to accept that our world is adherently real through the Realist Presupposition (RP). What we do not have reason to do is to reject the possibility of adherent unreality. RP licenses acceptance, not demonstrative exclusion.

   The sceptic’s argument therefore fails to generate any epistemic threat. It merely restates the conceptual point that adherent reality is not demonstrable; a point that follows from the definition of adherent reality itself.

2. The Anti‑Sceptic’s Modus Ponens

The anti‑sceptical response simply reverses the sceptic’s reasoning:

1.     If we know that the external world is real, then we can rule out sceptical alternatives.

2.     But we do know that the external world is real.

3.     Therefore, we can rule out sceptical alternatives.

At first glance, this seems compelling. It captures the intuition that sceptical hypotheses are idle: we do not seriously entertain the possibility that we are dreaming or deceived, and our epistemic practices proceed without hesitation.

Its fully explicit form is:

1.     If we know that the external world is adherently real, then we can rule out adherently real sceptical alternatives.

2.     But we do know that the external world is inherently real.

3.     Therefore, we can rule out adherently real sceptical alternatives.

The first premise must employ adherent reality, since sceptical scenarios concern the comparative status of worlds. The conclusion must also concern adherent reality, for the anti‑sceptic aims to exclude the possibility that our world is adherently unreal. But the second premise invokes inherent reality instead.[12] The argument equivocates between the two notions of reality, and the conclusion does not follow.

We can make the argument deductively valid:

1.     If we know that the external world is adherently real, then we can rule out adherently real sceptical alternatives.

2.     But we do know that the external world is adherently real.

3.     Therefore, we can rule out adherently real sceptical alternatives.

This argument is valid, but the second premise is flawed. RP licenses acceptance of adherent reality, but it is not strong enough to rule out the possibility that our world is not the adherently real world in sceptical scenarios. The kind of knowledge vindicated by RP is not conclusive knowledge.

   The anti‑sceptic’s intended conclusion, that we can demonstratively rule out sceptical alternatives, it is not merely unsupported; it is conceptually meaningless. It presupposes a framework in which adherent reality can be demonstrated from within a single world. But adherent reality is not the kind of status that can be defended under ordinary circumstances. The anti‑sceptic’s argument inherits the sceptic’s lack of conceptual scrutiny.

3. The Dialectical Collapse

The sceptical and anti‑sceptical arguments collapse for the same reason: both presuppose that reality is a single epistemic status. Both demand demonstrative proof of reality. Both assume that knowledge of reality requires the ability to exclude sceptical alternatives. Both are mistaken.

This collapse is not a refutation of scepticism but a dissolution. It shows that the sceptical problem arises only because we have failed to distinguish two senses of reality that play different roles in our epistemic lives. Once the distinction is in place, the sceptical demand for demonstrative certainty of adherent reality loses its force, and the anti‑sceptical attempt to provide such proof is revealed as equally misguided.

 

III. A Deepened View of the Realist Presupposition

The collapse of the classical sceptical dialectic leaves a residual question: how should we rationally proceed once we recognise that adherent reality cannot be demonstrated and, in ordinary circumstances, cannot even be assessed? The sceptic concludes that we must suspend judgment. The anti‑sceptic concludes that we must affirm the reality of the external world. Both conclusions inherit the conceptual mistake that generated the sceptical problem in the first place. Both assume that reality has a single epistemic status and that knowledge of reality requires demonstrative proof. Once the distinction between inherent and adherent reality is in place, neither conclusion can be sustained.

This section articulates the rational stance that remains once the conceptual confusion is removed. The stance is not inferential, evidential, or metaphysical. It is a presupposition forced by the structure of our epistemic situation. As introduced earlier, it is the Realist Presupposition (RP):

RP: In the absence of any evidence for a sceptical scenario, we are rationally entitled to assume that the external world is both inherently and adherently real.

RP is not a thesis about the ultimate nature of reality. It is not a claim that the external world is metaphysically fundamental, ontologically privileged, or uniquely actual. It is not a hypothesis to be tested or a conclusion to be defended. RP is a rational orientation, a stance that structures our epistemic practices once we recognize the limits of demonstrative proof and the conceptual inapplicability of adherent reality in ordinary circumstances.

1. What RP Is Not

To understand RP, we must first clarify what it is not. These clarifications pre‑empt several familiar objections and prevent RP from being misclassified.

RP is not dogmatic. It does not assert that sceptical alternatives are impossible, incoherent, or self‑defeating. It does not claim that sceptical scenarios violate logical or metaphysical constraints. RP does not foreclose sceptical possibilities; it merely refuses to treat them as live in the absence of evidence.

RP is not metaphysical. It does not claim that our world is metaphysically fundamental or uniquely actual. It does not attempt to settle the metaphysics of modality or the ontology of possible worlds.

RP is not inferential. It does not rely on usual inferences to the best explanation, probabilistic justification, or abductive reasoning. It is not a conclusion properly drawn from evidence.

RP is not psychological. It is not a description of how human beings happen to think. It is a normative stance grounded in the conceptual structure of rational doubt.

These clarifications block the objection that RP is merely pragmatism, merely dogmatism, or a disguised metaphysical thesis. RP is none of these. It is a structural requirement of rational epistemic practice once the inherent/adherent distinction is properly understood.

2. The Conditional Form of RP

RP has a distinctive conditional form:

In the absence of any evidence for a sceptical scenario…

This clause is essential. RP does not assert that sceptical scenarios are impossible or incoherent. It asserts only that sceptical hypotheses require evidential motivation. Without such motivation, sceptical doubt is empty.

The second clause is equally essential:

…we are rationally entitled to assume that the external world is both inherently and adherently real.

This clause does not assert that the external world is adherently real. It asserts only that we are rationally entitled to assume that it is. The entitlement is not inferential, evidential, or metaphysical. It is a presupposition allowed by the structure of our epistemic situation, more specifically, by the fact that adherent reality cannot be applied unless a sceptical scenario actually occurs.

RP, therefore, has a distinctive epistemic profile. It is neither a belief nor a hypothesis. It is a presupposition. It structures our epistemic practices without being the conclusion of any argument.

This clarification blocks the objection that RP is too weak (merely pragmatic) or too strong (dogmatic). RP is neither. It is structurally allowed.

 

IV. Grounds for the Realist Presupposition

RP, the realist presupposition, is supported by two independent considerations that arise naturally once the distinction between inherent and adherent reality is in place. The first concerns explanatory economy. The second concerns the structure of rational doubt. These considerations do not prove RP – nothing could prove RP, given the conceptual limits imposed by adherent reality. Rather, they show that RP is the rational stance to adopt once we recognize those limits. They pre‑empt the objection that RP is arbitrary or unjustified.

1. Explanatory Economy

The first ground for RP concerns explanatory economy. This point has historical roots in Russell’s observation that positing an external world is the simplest explanation of our experience (1912, chap. II). Jonathan Vogel (1990) later recast this insight using the machinery of inference to the best explanation (IBE): the ordinary hypothesis, that our world is the adherently real one, is explanatorily superior to any sceptical alternative, which would require ad hoc stipulations to preserve the appearances.

   Our conceptual distinction clarifies the precise force of this point. IBE does not prove adherent reality. It cannot prove adherent reality, because adherent reality is not demonstrable and, in ordinary circumstances, not even applicable. But IBE does support the rational assumption that our world is adherently real. It shows that the ordinary hypothesis is explanatorily preferable to sceptical alternatives because sceptical hypotheses require additional assumptions that are not motivated by experience, whereas the ordinary hypothesis is simpler, more direct, and more economical.

   This clarification blocks the familiar objection that IBE is insufficient to refute scepticism. RP does not use IBE to refute scepticism. It uses IBE to justify a presupposition.

2. The Structure of Sceptical Hypotheses

This point can be made more precise. A sceptical hypothesis must preserve the appearances. It must explain why our experience exhibits vividness, involuntariness, intersubjective checkability, and law‑governed regularity. It must explain why our epistemic practices succeed, why our scientific theories are predictively successful, and why our perceptual judgments are reliable. To do so, it must posit a complex system of deception, simulation, or manipulation. It must posit a structure that mirrors the structure of the external‑world hypothesis. It must posit additional mechanisms to preserve the appearances.

The ordinary hypothesis that our world is not only inherently but also (ceteris paribus) adherently real does not require these additional assumptions. It posits an external world that exhibits the structural features of experience and no deception, simulation, or manipulation. It posits no additional mechanisms. This makes it explanatorily superior. IBE therefore supports the rational assumption that our world is adherently real without proving adherent reality or meeting the sceptical demand for demonstrative certainty. It supports a presupposition, not a conclusion.

   This clarification blocks the objection that RP overreaches by converting explanatory preference into knowledge.

3. The Structure of Rational Doubt

The second ground for RP concerns the structure of rational doubt. This point has roots in Wittgenstein’s observation that doubt is intelligible only against a background of certainty (1969). A sceptical hypothesis requires evidential motivation. Without such motivation, the doubt is empty. It cannot be meaningfully entertained.

   Our conceptual distinction clarifies the precise force of this point. Sceptical hypotheses concern adherent reality; they concern the status of our world relative to other possible worlds; they require evidential motivation. Without such motivation, they cannot be meaningfully entertained. They are not live possibilities. They are idle.

   This clarification blocks the objection that sceptical hypotheses can be entertained without evidence.

4. The Inapplicability of Adherent Reality

This point can be made more precise. To doubt that our world is adherently real, we would need evidence that our world is a simulation, deception, or inferior alternative, that is, we would need the evidence that our world is not the “actual” world. We would need evidence that our world stands in the wrong relation to other possible worlds. But we possess no such evidence: no evidence of deception, simulation, or manipulation. Without such evidence, sceptical doubt is empty. It cannot be meaningfully entertained. RP therefore remains undefeated. The recognition that sceptical hypotheses require evidential motivation, and that we possess none, is crucial. It shows that RP is a rational stance forced by the structure of rational doubt.

   This clarification blocks the objection that RP is optional or arbitrary.

5. The Convergence of the Two Grounds

These two grounds – explanatory economy and the structure of rational doubt – converge. They support RP from different directions. They show that RP is not arbitrary, dogmatic, or metaphysical. RP is the rational orientation that structures our epistemic practices once the conceptual confusion is removed.

   The convergence is not accidental. It reflects a structural feature of our epistemic situation. We inhabit one world, and only one world is ever accessible. We cannot compare our world with other possible worlds. We cannot determine whether our world is the “actual” world rather than a simulation or deception, except in a logically conceivable (though perhaps physically impossible) radical sceptical scenario. Adherent reality is not demonstrable and, in ordinary circumstances, not even applicable. Sceptical hypotheses require evidential motivation. Without such motivation, they are empty. Explanatory economy supports the rational assumption that our world is adherently real. The structure of rational doubt supports the rational entitlement to assume adherent reality.

   The two grounds converge. RP is the stance that remains once the conceptual confusion is removed. It is the rational orientation that structures our epistemic practices once we recognise the limits of demonstrative proof.

 

V. Conclusions

The argument of this paper has proceeded by conceptual clarification rather than empirical investigation or metaphysical speculation. The dissolution of scepticism is not achieved by showing that sceptical hypotheses are improbable, explanatorily inferior, pragmatically irrelevant, or logically inconsistent. It is achieved by recognizing that the sceptical demand for demonstrative certainty rests on a category mistake. The sceptic asks for proof of adherent reality, but adherent reality has no demonstrable status. In our ordinary circumstances, it is not even applicable, because its assessment requires comparison across worlds, and only one world is ever accessible, except in logically conceivable sceptical scenarios whose empirical possibility remains unknown. The anti‑sceptic inherits the same mistake by attempting to provide such proof. Both sides of the traditional dialectic misfire because both assume that reality has a single epistemic status.

   By contrast, inherent reality is demonstrable. Section I showed that inherent reality is given in the structure of experience itself. The criteria of vividness, involuntariness, intersubjective checkability, law‑governed regularity, and contextual coherence through time form a mutually reinforcing pattern that makes the attribution of inherent reality unavoidable. These criteria apply not only to directly perceived objects but also to indirectly accessible entities, from remote nebulae to subatomic particles, whose causal integration with observable phenomena justifies their inclusion within the domain of inherent reality. Once these criteria are properly understood, they yield a straightforward proof of the external world: the totality of things that satisfy the criteria of external reality, whether directly perceived, indirectly detected, or known through testimony. This is why inherent reality is epistemically secure.

   This result stands in sharp contrast to Carnap’s view that the existence of the external world is a pragmatic fiat. Our analysis shows that the existence of the external world is not a matter of linguistic choice or practical convenience. It is demonstrable because inherent reality is given in the very conditions of intelligible experience. The sceptic cannot coherently deny inherent reality, for the denial would undermine the conditions under which sceptical reasoning is possible.

   Once the conceptual confusion between inherent and adherent reality is removed, we must adopt a stance that structures our epistemic practices. The Realist Presupposition (RP) is the stance that remains. RP is supported by two independent considerations. Explanatory economy shows that the ordinary hypothesis – that our world is the adherently real one – is explanatorily superior to sceptical alternatives, which require ad hoc stipulations to preserve the appearances. The structure of rational doubt shows that sceptical hypotheses require evidential motivation, and that without such motivation, sceptical doubt is empty. These considerations do not prove RP; they vindicate it. They show that RP is the rational stance to adopt once we recognize the limits of demonstrative proof and the conceptual inapplicability of reasoning for or against adherent reality in ordinary circumstances.

   The conceptual distinction between inherent and adherent reality has profound epistemological consequences. It clarifies what can and cannot be demonstrated, the limits of rational doubt, the structure of epistemic entitlement, the role of presuppositions in epistemic practice, the nature of the sceptical problem, and the rational stance that remains once the conceptual confusion is removed.

   Most importantly, it clarifies why the sceptical dialectic cannot be repaired. Once reality is recognized as conceptually bifurcated, the sceptic cannot reformulate the problem in terms of adherent reality alone, for adherent reality is not demonstrable and not applicable in ordinary circumstances. Nor can the anti‑sceptic reformulate the response in terms of inherent reality alone, for inherent reality is not the status at issue in sceptical scenarios. The dialectic collapses because its presupposition – the univocity of reality – is untenable. What remains is not a refutation of scepticism but a dissolution: the sceptical problem cannot be coherently formulated once the conceptual distinction is in place.

 

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[1] We say “defeasible” because Carnap’s pragmatic construal of external‑world existence has been criticized by Strawson (1963: 503–518) and Stroud (1984: 170–208), who argue that by denying cognitive status to external‑existence claims, Carnap leaves us without any account of how we know that the external world is real.

[2] Philosophers have historically regarded the notion of reality as primitive and univocal, not as a concept open to analytical decomposition. As a result, the distinction was never drawn: the inherited epistemological framework treated “reality” as a single, fundamental epistemic status, thereby obscuring the internal structure that makes the inherent/adherent distinction possible.

 

[3] As Wittgenstein noted, “Criteria give our words their common meaning.” (1958: 57).

[4] These criteria were already partially considered in the philosophical tradition by (at least) Locke (1689), Berkeley (1710), Hume (1739), Kant (1781), J. S. Mill (1889),  Gottlob Frege (1918) and G. E. Moore (1953).

[5] The most explicit classical articulation of these criteria is found in Berkeley’s Principles of Human Knowledge, Part I, §§29–33. In these sections, Berkeley distinguishes sensory ideas from ideas of imagination by emphasising their greater vividness and determinacy, their resistance to voluntary control, their availability to other perceivers, and their conformity to stable causal and temporal patterns. Although Berkeley does not present these features as a formal list, the cluster of properties he attributes to sensory ideas in this portion of the Principles constitutes the canonical source for the modern reconstruction of these criteria.

[6] Laurence BonJour, analysing Locke’s claim that we know external objects because our perceptions are vivid, involuntary, coherent, and causally dependent on external objects, argued that these features do not suffice to justify belief in an external world (2010; Ch. 4, §4.2). But he considers these conditions separately. He does not saw their cumulative character. Being coherently satisfied through enough time, the five above-considered criteria inevitably suffice for a kind of attribution of reality that remains even within a sceptical scenario. This is the kind of reality I call inherent.

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[7] If one insists on taking seriously Putnam’s argument against the possibility that we are brains in vats (1981, chap. 1), one may substitute another sceptical hypothesis – such as dreaming or coherent hallucination – since nothing essential turns on the specific choice of the BIV scenario (see DeRose & Warfield 1999, Introduction, pp. 1–3).

[8] I am not claiming they are physically possible. My claim is that we can use these thought experiments to clarify our concept of adherent reality as conceived in sceptical scenarios.

[9] Experiments with artificial reality, such as the integration of neural‑input devices like the Mudra wristband with AR glasses, reinforce the central point of the distinction. These systems already generate environments that are, to a significant extent, inherently real: they exhibit vividness, independence, virtual intersubjectivity, perceptual coherence, causal responsiveness, and experiential stability from within the user’s standpoint. Nevertheless, these environments remain adherently unreal because their ontological status is derivative: they are produced, sustained, and delimited by the physical world, which is inherently and presumably adherently real as well. The artificial environments depend on our world as their generative substrate and cannot exist independently of it. Their reality is therefore comparative and subordinate.

[10] Although definitionally very different, the present distinction has its origins in reflections on Carnap’s (1950) contrast between internal and external questions of existence, where he suggested that the existence of the external world as a whole cannot be proved. In my view, he was confusing his own external question of existence with the adherent question of reality. On our account, the inherent reality of the world as a whole can be established as a summation of its items, whereas adherent reality, though not provable, can still be shown to be the most rational stance.

[11] The lack of distinction between inherent and adherent reality also limits the force of O. K. Bouwsma’s well‑known critique of the evil‑demon hypothesis (1949). Bouwsma argues that the demon’s “illusion” would simply become the subject’s reality, but this holds only for inherent reality. Once adherent reality is distinguished, the demon can still deceive at the comparative level, and Bouwsma’s dissolution no longer undermines the sceptical argument.

[12] Moore’s “proof” of the external world (1962) hinges on a conflation between inherent and adherent reality. By raising his two hands, he shows only that the world is inherently real—our experience has the ordinary marks of reality. But this gesture does nothing to establish the world’s adherent reality, that is, its standing in the relevant comparative relation to other possible worlds. Moore proves inherent reality, but adherent reality remains unaddressed.