Can Philosophical Scepticism Be Refuted?
Philosophical scepticism can be refuted. Descartes' a priori deduction fails due to circularity, and Russell's best hypothesis argument concedes too much by treating the external world as a hypothesis. Wittgenstein successfully refutes scepticism by showing that genuine doubt requires reasons and circumstances, and that the sceptic's doubt is not a purer form of doubt but no doubt at all
- Philosophical scepticism is the view that knowledge of the external world is impossible. It does not merely claim we sometimes make mistakes — it claims that even our most carefully considered beliefs about mind-independent physical objects can never be known with certainty, because there is always a logically possible scenario in which those beliefs are false - The most powerful version is Descartes' external world scepticism, developed through his method of doubt. Descartes imagines an evil demon of supreme power and cunning whose sole purpose is to deceive him about everything — including the existence of physical objects, other minds, and even mathematical truths. Since this scenario is logically possible, no belief about the external world can be held with certainty - I will consider three attempts to refute external world scepticism: Descartes' own a priori deduction of the external world's existence, Russell's argument that the external world is the best hypothesis available, and Wittgenstein's argument that scepticism is nonsensical because genuine doubt requires reasons and circumstances. I will argue that while the first two fail, Wittgenstein successfully refutes philosophical scepticism
Section 1: Descartes' A Priori Deduction
- Descartes' deduction is ambitious and philosophically interesting — the attempt to use a priori reasoning to guarantee the reliability of perception is a serious philosophical project. The trademark argument and the proof of God's benevolence have genuine philosophical content that cannot simply be dismissed - However the argument is fatally undermined by the Cartesian circle and by the fact that it does not genuinely eliminate the evil demon. A sceptic can accept everything Descartes says about God and still maintain that the evil demon scenario has not been ruled out. The argument therefore fails as a refutation of scepticism — it cannot provide the certainty it promises
Descartes: Descartes' a priori deduction of the external world
- Having established through the cogito that he exists as a thinking thing, Descartes attempts to prove the external world exists through an a priori deductive chain. He first argues that God exists through the trademark argument — he has an idea of a supremely perfect being, and the causal adequacy principle entails that only a supremely perfect being could have caused this idea in his finite mind. God therefore exists - He then argues that God, being supremely good and perfect, would not deceive him. His perceptual experiences of physical objects are involuntary — they do not originate in his own will. If physical objects did not exist, God would be allowing him to be systematically deceived about their existence with no means of detecting this deception. But a perfectly good God would not permit this. Therefore, the cause of his involuntary perceptual experiences must be physical objects, and an external world of physical objects exists - This is an attempt to defeat scepticism from within Descartes' own framework — using the certainty established by the cogito and God's existence to guarantee the reliability of perception
: The sceptical response — the Cartesian circle and the evil demon
- The argument fails because it is circular in a way that directly undermines its anti-sceptical purpose. Descartes uses the evil demon hypothesis in the first wave of doubt to motivate the project of finding certainty. But his proof of God's existence — which is supposed to rule out the evil demon — itself relies on clear and distinct ideas whose reliability has not yet been established. The Cartesian circle means the argument assumes what it sets out to prove - More directly, a sceptic can simply point out that Descartes has not eliminated the evil demon — he has merely asserted that God would not permit such deception. But the evil demon scenario is logically possible regardless of God's existence. If an evil demon exists alongside God, or if the argument for God's existence is flawed, the evil demon remains a genuine possibility and external world scepticism is not defeated - Crucially, the premise that involuntary perceptual experiences can only be caused by God or physical objects is precisely what the evil demon hypothesis denies. Descartes cannot use this premise to rule out the evil demon without already assuming the demon does not exist — which is what the argument was supposed to establish
Section 2: Russell's Best Hypothesis and Moore's Direct Proof
- Moore's argument is too quick. The sceptic will not be impressed by a demonstration that simply assumes the reliability of perception, which is precisely what is in question. However Moore is right that our ordinary certainties feel more secure than philosophical hypotheses, and this intuition anticipates Wittgenstein's more sophisticated treatment - Russell's argument is genuinely stronger than Descartes' and is the right kind of response — proportionate to the evidence and making no claims to impossible certainty. But it concedes too much to the sceptic by treating 'the external world exists' as a hypothesis that could in principle be false. This is precisely the assumption Wittgenstein will challenge in Section 3
Moore: Moore's direct proof of the external world
- G. E. Moore offers a direct and strikingly simple attempt to prove the external world exists. He holds up his two hands and argues: here is one hand, here is another, therefore at least two physical objects exist, therefore an external world exists. Moore claims this is a perfectly rigorous proof — the premises are more certain than any sceptical argument, so the proof establishes its conclusion beyond doubt - Moore's argument is an attempt to defeat scepticism by direct demonstration rather than philosophical argument. He insists that our common-sense knowledge of the external world is more certain than any philosophical hypothesis that calls it into question, and that the sceptic's doubt is therefore less well-grounded than our ordinary knowledge
Russell: Russell's best hypothesis argument
- Russell offers a more sophisticated version of the anti-sceptical move. He argues that the existence of physical objects as the cause of our sense experiences is the best available hypothesis — the simplest and most explanatorily powerful account of why we have the sensory experiences we do. This is an abductive argument, an inference to the best explanation: physical objects explain our experiences better than any alternative, including the evil demon - Russell is not claiming certainty — he explicitly acknowledges that the external world hypothesis might be false. His point is that it is the most reasonable belief available given the evidence, and that we are justified in holding it on those grounds. This is a more modest and proportionate response to scepticism than Descartes' attempt at deductive certainty
: The sceptical response — reasonableness is not certainty
- Moore's argument fails as a refutation of scepticism because it simply assumes what the sceptic is calling into question. The sceptic's challenge is precisely whether we can know that we have hands — Moore cannot defeat this by holding up his hands and asserting certainty. The argument begs the question - Russell's argument is stronger but still does not fully refute scepticism. The sceptic never claimed that the external world hypothesis is unreasonable — only that it cannot be known with certainty. Russell can establish that belief in the external world is the most reasonable hypothesis, but a reasonable hypothesis can still be false. As long as the evil demon scenario remains logically possible, scepticism has not been ruled out. Russell's argument shows our belief is probable, not certain — and scepticism is a claim about certainty
Section 3: Wittgenstein's Dissolution of Scepticism
- Wittgenstein's argument is initially difficult to grasp but becomes compelling on reflection. The point that genuine doubt requires reasons and circumstances is not a restriction on philosophical thinking — it is an observation about what doubting actually is. To strip doubt of all context and reasons is not to produce a purer, more philosophical form of doubt; it is to produce something that no longer functions as doubt at all - The hinge propositions point is the deeper and more powerful move. It explains why both Descartes and Russell went wrong: Descartes tried to prove a hinge proposition by deduction, and Russell tried to treat it as an empirical hypothesis. Both mistakes arise from misidentifying the logical status of 'the external world exists.' Wittgenstein shows that this proposition is not the kind of thing that can be proved, disproved, or confirmed — it underlies all proof, disproof, and confirmation - A possible objection is that Wittgenstein is merely restricting himself to how ordinary language works rather than engaging with the genuine philosophical problem. But this objection misunderstands the argument. Wittgenstein is not saying 'ordinary people don't doubt the external world so we shouldn't either.' He is saying that the very concept of doubt has conditions of application, and the sceptic's doubt fails to meet them. This is a philosophical point about the nature of doubt, not a conservative appeal to common sense - Wittgenstein's refutation is more successful than Russell's because it does not merely show that scepticism is unreasonable — it shows that scepticism is unintelligible. The sceptic is not making a false claim; they are failing to make any claim at all
Wittgenstein: Wittgenstein's dissolution — genuine doubt requires reasons and hinge propositions cannot be doubted
- Wittgenstein's response to scepticism, developed in On Certainty, is fundamentally different in kind from Descartes' and Russell's. Rather than trying to prove that the external world exists, Wittgenstein argues that the sceptic's doubt is not genuinely intelligible — that philosophical scepticism does not pose a real question that requires a real answer - Wittgenstein begins from the observation that in ordinary life, doubt is always contextual and reason-dependent. We can sensibly doubt specific claims when there is some reason to doubt them — a reason arising from particular circumstances. I can doubt whether there is milk in the fridge if I cannot remember buying any. I cannot sensibly doubt whether I have hands in circumstances where there is nothing to prompt such a doubt. Doubt, to be genuine doubt, requires a context that gives it content - The sceptic, however, claims to doubt everything about the external world simultaneously, without any particular reason or circumstance that motivates the doubt. Wittgenstein argues this is not real doubt — it is the word 'doubt' being used without the circumstances that give doubting its meaning. Just as I cannot sensibly doubt that 2 + 2 = 4 simply by uttering 'perhaps 2 + 2 ≠ 4', I cannot genuinely doubt the existence of the external world simply by uttering 'perhaps the external world does not exist' - Underlying this point is Wittgenstein's notion of hinge propositions. Some propositions — like 'the external world exists', 'I have a body', 'the past really happened' — do not function as ordinary empirical claims that can be confirmed or disconfirmed by evidence. Instead they function as the framework within which all questioning, doubting, and investigating takes place. They are the hinges on which our entire practice of inquiry turns. To doubt a hinge proposition would be to undermine the very practice of doubting itself — like trying to use a ruler to check whether the ruler is accurate. These propositions are not known in the ordinary sense, but neither are they doubted. They stand fast, not because we have proved them, but because they are presupposed by everything we do and say - This is why Russell's treatment of 'the external world exists' as a hypothesis is mistaken. A hypothesis is something that can in principle be confirmed or disconfirmed by evidence. But 'the external world exists' is presupposed by all evidence gathering — you cannot gather evidence without already taking the external world for granted. It is not a hypothesis at all, and so the question of whether it is the best hypothesis does not arise
- Descartes' a priori deduction fails: the argument is circular and does not eliminate the evil demon, which was the hypothesis it was supposed to overcome - Russell's best hypothesis argument is stronger and more proportionate, but it concedes too much — treating 'the external world exists' as a hypothesis that could in principle be false leaves scepticism undefeated, since the sceptic never denied the hypothesis was reasonable, only that it was certain - Wittgenstein successfully refutes scepticism by showing that genuine doubt requires reasons and circumstances, and that 'the external world exists' is not an empirical hypothesis at all but a hinge proposition that underlies all inquiry. The sceptic's doubt is not a purer philosophical form of doubt — it is the word 'doubt' used without the conditions that give it meaning. Philosophical scepticism is therefore not defeated but dissolved