Additional reflections on Putnam, Wright and Brains in Vats

Putnam’s argument against the sceptical Brain-in-a-Vat hypothesis continues to intrigue. I argue in what follows that the argument refutes a particular kind of sceptic and make a proposal about its more general significance. To appreciate the soundness of the argument, I explain, we need to appreciate that the sceptic’s contention is that I cannot know that I am not a brain in a vat even if I am not. This is why in response to the sceptic it is legitimate to make a transition from knowing that a sentence is true to knowing the truth it expresses, which is the crucial move in the argument

The passage of time

Eric Olson argues that the dynamic view of time must be false. It requires that the question ‘How fast does time pass?’ has an answer. But its only possible answer, one second per second, is not an answer. I argue that Olson has failed to identify what is wrong with talk of time’s passage. Then I argue that, nonetheless, he is right to reject it. To say that time passes is analogous to saying that space is dense, and to ask about the rate of time’s passage is analogous to asking how dense space is. Since the questions are on a par the dynamic view of time, which requires that they are not, is mistaken

The Great Western Railway

In On The Plurality of Worlds Lewis presents the case of the Great Western Railway as a candidate counter-example, along with the usual suspects, to the thesis that two things cannot be in the same place at the same time. Typically, pluralists or many-thingers, i.e., those who reject the thesis, point to modal or historical or aesthetic differences to justify their judgement of non-identity. Lewis’s aim to is to show the inadequacy of this justification, at least as regards modal differences, by considering a case in which it clearly fails, in which the judgement of non-identity so based is incredible, and hence to make it evident that in all such cases the appeal to modal differences is insufficient. What makes the case of the Great Western Railway special is that it is a purely spatial example, as Lewis emphasises. In what follows I set out the example and try to make it clear that, as Lewis says, for this reason a judgement of non-identity based on an appeal to modal differences is incredible. Then I give another example, easier to understand, I think, which makes the same point, inspired by Russell’s famous joke about the irate yacht owner

Two-boxing is irrational

Philosophers debate whether one-boxing or two-boxing is the rational act in a Newcomb situation. I shall argue that one-boxing is the only rational choice. This is so because there is no intelligible aim by reference to which you can justify the choice of two-boxing over one-boxing once you have come to think that you will two-box (whereas there is such an aim by reference to which you can justify one-boxing). The only aim by which the agent in the Newcomb situation can justify his two-boxing is the subjunctively described aim of ‘getting more than I would if I were to one-box’. But such a subjunctively described aim can justify an action only if it can be seen as generating, in conjunction with the agent’s beliefs, an indicatively describable aim which justifies the action. In the case of the Newcomb agent the aim of 'getting more than I would if I were to one-box’ cannot be seen in this way

From Essence to Metaphysical Modality?

How can we acquire knowledge of metaphysical modality? How can someone come to know that he could have been elsewhere right now, or an accountant rather than a philosophy teacher, but could not have been a turnip? In his (2018) Jago proposes an account of a route to knowledge of the way things could have been and must be. He argues that we can move to knowledge of metaphysical modality from knowledge about essence. In his (2019) Curtis rejects Jago’s explanation. It cannot, he argues, explain our knowledge of de re necessity. We agree. But there is more to be said. To give an account of our knowledge of metaphysical necessity is part of the task Jago set himself. But another part is to give an account of the knowledge of the (non-actual) possibilities accorded to particular objects (Jago 2018: 12). And prior to both what is needed, and something Jago attempts to supply, is an account of how ordinary knowers can come to have knowledge of an individual’s essential properties. We argue that Jago’s accounts of both these additional matters are also unsatisfactory. This is important because the thought that our knowledge of metaphysical modality has its source in our knowledge of essence is currently an attractive one and Jago has set out very clearly what must be done to justify the thought. The flaws in his proposal thus indicate the work needed if the attractive thought is to be accepted

Presentism, Endurance and Object-Dependence

According to the presentist the present time is the only one that there is. Nevertheless, things persist. Most presentists think that things persist by enduring. Employing Jonathan Lowe’s notion of identity-dependence, Tallant argues that presentism is incompatible with any notion of persistence, even endurance. This consequence of Lowe’s ideas, if soundly drawn, is important. The presentist who chooses to deny persistence outright is a desperate figure. However, though Lowe’s notion is a legitimate and worthwhile one, this application is faulty. The incompatibility of presentism and persistence is not part of Lowe’s heritage. A positive conclusion can be drawn. A form of persistence is compatible with presentism. It is one on which persistence is defined in tensed terms using an adverbial tense operator: x persists iff x exists and existed or will exist. Unsurprisingly, so understood persistence is endurance. The commonly held view is correct