Counterfactual reasoning and knowledge of possibilities

Philosophical Studies, Aug 2016

Williamson has argued against scepticism concerning our metaphysically modal knowledge, by arguing that standard patterns of suppositional reasoning to counterfactual conclusions provide reliable sources of correct ascriptions of possibility and necessity. The paper argues that, while Williamson’s claims relating to necessity may well be right, he has not provided adequate reasons for thinking that the familiar modes of counterfactual reasoning to which he points generalise to provide a decent route to ascriptions of possibility. The paper also explores another path to ascriptions of possibility that may be extracted from Williamson’s ideas, before briefly considering the general status of counterfactual reasoning in relation to our knowledge of possibilities.

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Counterfactual reasoning and knowledge of possibilities

Philosophical Studies April 2017, Volume 174, Issue 4, pp 821–835 | Cite as Counterfactual reasoning and knowledge of possibilities AuthorsAuthors and affiliations Dominic Gregory Open Access Article First Online: 18 August 2016 3 Shares 1.9k Downloads 1 Citations Abstract Williamson has argued against scepticism concerning our metaphysically modal knowledge, by arguing that standard patterns of suppositional reasoning to counterfactual conclusions provide reliable sources of correct ascriptions of possibility and necessity. The paper argues that, while Williamson’s claims relating to necessity may well be right, he has not provided adequate reasons for thinking that the familiar modes of counterfactual reasoning to which he points generalise to provide a decent route to ascriptions of possibility. The paper also explores another path to ascriptions of possibility that may be extracted from Williamson’s ideas, before briefly considering the general status of counterfactual reasoning in relation to our knowledge of possibilities. KeywordsModal epistemology Possibility Counterfactuals Suppositions Knowledge Williamson  1 Introduction We know that it is not just true that 2 + 2 = 4, but that it could not be false that 2 + 2 = 4; and we know that, although there are currently over 7 billion people living on the surface of this planet, there could have been under 3 million. The proposition that 2 + 2 = 4 is thus metaphysically necessary, while the proposition that there are under 3 million people living on the earth at the current time is metaphysically possible. How do we get our knowledge that certain propositions are not just actually true but necessary? And how do we get our knowledge that certain propositions which are actually false yet could have been true? In relatively recent work, Williamson has sought to shed light on our ascriptions of the metaphysical modalities.1 He suggests that philosophical appeals to, say, intuition as a source of our beliefs about (metaphysical2) possibility and necessity arise from a failure to see the wider context within which our thoughts about the metaphysical modalities take place, and that they thereby make our claims to metaphysically modal knowledge seem needlessly shady. Rather, he argues, ‘the ordinary cognitive capacity to handle counterfactual conditionals carries with it the cognitive capacity to handle metaphysical modality’ (Williamson 2007b, 136). The following two sections present Williamson’s views in more detail. Section 2 presents some background materials relating to the epistemology of counterfactuals and their negations, while Sect. 3 explains how Williamson extends those materials to generate ideas relating to our ascriptions of the metaphysical modalities. Sections 4 and 5 argue against Williamson’s claim to have drawn the sting from scepticism about our knowledge of what is metaphysically possible, by having shown that the reliability of certain forms of argument leading to ascriptions of possibility is a mere corollary of the reliability of a more general pattern of reasoning that we habitually employ in support of denials of counterfactual conditionals. Section 6 then explores another potential route to ascriptions of possibility that is easily extracted from Williamson’s ideas. Section 7 concludes: it suggests that, while counterfactual reasoning doubtless has crucial roles to play in extending our prior knowledge of possibilities, the amount of philosophical light that it can shed upon our knowledge of possibility in general is limited. 2 Williamson on counterfactual knowledge Suppose that one wishes to assess whether, if A were to be the case, B would be too (‘A \(\boxright\) B’). Williamson notes that one might ‘schematise a typical overall process of evaluating a counterfactual conditional thus: one supposes the antecedent and develops the supposition… To a first approximation: one asserts the counterfactual conditional if and only if the development eventually leads one to add the consequent’ (Williamson 2007b, 152–153). But, as Williamson remarks, this schematisation oversimplifies things somewhat, because we often rehearse a variety of scenarios in which the antecedent of a given counterfactual conditional obtains. We may consider various different scenarios in which the antecedent holds good, yet which are all pretty close to actuality, checking to see whether the consequent continues to obtain under those slight variations in the initial conditions. ‘Robustness in the result under such minor perturbations supports a higher degree of confidence’ (Williamson 2007b, 153) in the truth of the relevant counterfactual conditional, by suggesting that the consequent flows from the antecedent in a relatively wide range of possible circumstances. Suppose that, after running through a range of iterations of the above process using the propositions A and B, we find that our developments of initial suppositio (...truncated)


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Dominic Gregory. Counterfactual reasoning and knowledge of possibilities, Philosophical Studies, 2016, pp. 821-835, Volume 174, Issue 4, DOI: 10.1007/s11098-016-0707-2