Geach has claimed that Frege had an insight about number which should have led him to the doctrine of relative identity:

The subject of time travel has been receiving increasing attention in the recent philosophical literature. Most of the articles that deal with it have been concerned to defend the logical consistency of time travel against those who claim that it entails one or more contradictions. Two sorts of defences have been offered. The first sort of defence involves showing that time travel does not entail those consequences which other philosophers allege it does entail. The second sort of defence involves an admission that time travel does indeed involve that which its opponents allege it does involve, e.g., being in more than one place at a time, but arguing that such consequences in no way vitiate the logical consistency of this notion.

My first aim in this paper is to provide a defence of time travel of the second sort. More specifically, I want to cut the ground from under an argument which might run thus:

For quite a long time now I have argued against the view, widely held, and forcefully expounded by John Burnet, that at Phaedo 102b2-d2 Plato is formulating the notion of essential attribute and contrasting essence with accident. I have claimed that the essence-accident contrast is absent from that passage. This is a view that others have also held. But I have since 1950 found in that passage (as well as in some preceding ones) a formidable theory of relations. Recently, Professor David Gallop has taken me to task for my heterodoxy. His reaction is overwhelming:

Gallop's paper is very tantalizing. Although he establishes neither A nor B, he does offer a series of very extraordinary arguments, whose examination reveals the depth of Plato's thinking on relations.

In replying to my criticism of his interpretation of this passage, Professor H-N. Castañeda has disregarded much of my argument. In particular, he has ignored my contention that a contrast between 'essential’ and ‘accidental’ predication is integral to the wider argument for immortality in which Phaedo 102b-d is embedded. This would remain the case whatever the grammar of 102b-c, and whatever the exact force of πεφυxέναι and τυγχάνει at 102c1-2. Further, Castañeda pays no heed to the difficulty of interpreting Plato's other relational examples in his way, given that no analysis parallel to that of 102b-d is anywhere hinted at for them. Moreover, he disregards the difficulty that several other examples in the nearby context are analysed in terms of the Theory of Forms, and yet are not overtly ‘relational’ in the usual sense at all.

Castañeda says (note 12) that it is ‘clear’ from my own translation of several passages (72e6, 103e7, 109d4, 110b2, 111c2, etc.) that τυΥχάνει in the Phaedo ‘has nothing to do with accident.’

The problem of the Cartesian Circle has been with us ever since the publication of the Meditations. This is quite remarkable, since the error of circularity which Descartes is accused of having committed is not a subtle one but is, if there is such an error, a gigantic blunder which is not difficult to discover, which was pointed out to Descartes shortly after the Meditations appeared, and which completely undermines Descartes’ primary project, the establishment of sure and certain knowledge. It is incredible that Descartes, a slow and careful thinker with considerable philosophical talent, could have made such an obvious and egregious error. It is much more plausible that there really is no circularity in Descartes’ argument, and that the charges of circularity grow out of a misunderstanding of Descartes’ intention or of the way in which his argument progresses.

The incredible, of course, is possible, and I am not proposing that the question of the circle be resolved merely by dismissing it, nor am I suggesting that the text be ignored in order to force consistency onto Descartes’ thought.

Those who disturb the hornets’ nest better be thick skinned. Keeping that in mind, thus far I kept my silence in the face of the adverse reactions my essay “On What One Knows” has provoked in the literature. As to the merits of the various objections, moreover, I trusted the judgement of the philosophical community to sort them out, and either recognize their futility, or make the necessary adjustments in my arguments without the need to reject the conclusions.

In the case of Dunn and Suter, however, I decided to make an exception. The reason is that they indeed succeeded in pointing out certain difficulties in my position, which are not due to misunderstandings, conflicting linguistic intuitions, or other superficial sources. And, second, meeting their objections gives me the opportunity of proposing a significant refinement of my theory, the need for which I increasingly felt in the meanwhile myself.

Berkeley's idealism consists of the following claims. Objects such as chairs, apples, mountains, and our bodies are combinations of sensible qualities. Sensible qualities and combinations of such are ideas or sensations. In the philosophical sense of ‘substance’ there is no such entity as a substance. There are minds which perceive and will: When a mind perceives it has sensations or ideas; and when a mind wills it produces or causes sensations or ideas. These claims are grounded in the ontological and epistemological framework of assumptions, distinctions and arguments informing Berkeley's doctrine that esse est percipi aut percipere. The purpose of this paper is to explore and expose the main features of that framework.

What is the ontological force and import on Berkeley's claim that esse est percipi? One influential recent suggestion1 is this: Berkeley holds that (1) material substances do not exist, (2) the analysis of sensible things yields nothing but sensible qualities, (3) minds are mental substances and (4) no sensible quality or collection of sensible qualities can exist without inhering in some substance.

It is immensely difficult to give a philosophically adequate account of mental imagery. Peter F.R. Haynes (Mental Imagery, this Journal 6 [1976), pp. 709–19) objects to the standard accounts, and offers one of his own which avoids the standard difficulties. Unfortunately it in turn seems to lapse into incoherence.

Haynes rejects Cartesian accounts which would make images private objects in non-physical space. He also rejects current alternative views: both Rylean or behaviourist ones; and also intentionally complex ones, which assert that the relevant terms change their meaning (so that “red” means something different when applied to red balls and red images). He thinks that J. J. C. Smart's “topic neutral” approach may supply “the basis for a correct, intentionally simple, intuitively satisfying account of mental imagery” (p. 707). But an adequate account must also be neutral, as Smart's is not, between different theories of mind (pp. 707–8). In addition to avoiding these difficulties an adequate theory has certain other desiderata; in particular Haynes places valuable emphasis on the need to explain the fact that we can sometimes mistake images for real perceptions or, more real perceptions for images.

Not so long ago it was fashionable to claim that it is not the moral philosopher's business to say what things are good or what actions we should perform. This view is succinctly stated by A. J. Ayer:

On the other hand, in direct opposition to this, recently many philosophers actively moralize, in the sense that they argue for substantive normative ethical positions. In doing this they tend to assume but not to explore seriously two views: (1) that the notion of moral expertise is unproblematic, and (2) that moral philosophers in particular are moral experts. My aim in this paper is to promote the exploration of these questions. (1) is logically prior to (2). Nevertheless I begin with discussing (2); for puzzles about expertise in morals naturally emerge when one examines the credentials of candidates for the job.

1. What is the Problem of Personal Identity?

Locke posed the problem of personal identity in one brief question, “What makes the same person?” This formulation is deceptively simple. My aim is to offer a new interpretation of the problem and to suggest a method for finding a solution.

Investigations of personal identity are usually cast in terms of finding the criterion for personal identity. Yet talk of criteria is ambiguous. In one sense of the term, the criterion of personal identity would be special evidence for personal identity. According to the second usage, the criterion of personal identity would be that state of affairs for which evidence for personal identity is evidence. We will not be concerned with the first construal. On that reading, the problem of personal identity would be an epistemological issue. But the basic question concerning personal identity, “What is one person?” does not appear to be an epistemological question.

In his article, “Stroll on Russell's ‘Proof’” (this Journal VI, (1976), Robert Fahrnkopf takes issue with four comments I made about Russell's theory of descriptions in a paper, “Russell's ‘Proof,’” which appeared in the June 1975 issue of this Journal. Though I disagree with Fahrnkopf on the points in question, there would be no point in washing our private conceptual linen in a public place were it not for the ingenious and highly original suggestions he makes in his defense of Russell. I think some additional discussion may be useful in carrying the current debate about the theory a step further. In what follows, I will therefore deal with each of the four points he speaks to.

Suppose we live in a very advanced age of neurosurgical skills. We have a patient, Jones, with intractable pain. We have a second patient, Smith, with a long history of unintentional self-injury due to congenital absence of pain centres. So we decide to do double service by transplanting Jones's pain centres into Smith's brain.

Suppose we are able to transplant Jones's pain centres into Smith's brain. Half way through the operation we test the pain centres by stimulating them electrically in vitro. Would there be pain? Roland Puccetti argues that there would not be. Because (a) pains must have owners and (b) the only available candidate for that role — the excised tissue — is logically unfit to play it. He concludes that the firing of such centres in a normally functioning brain cannot be pain either and that, therefore, materialism is false.

So far as I can see, Puccetti's “refutation” is a series of nonsequiturs from start to finish, and that is what I mainly want to show. It will not follow, of course, that materialism is true. Indeed, I think the view which Puccetti attacks under that name is too naive to be taken seriously by anyone.

Glenn Pearce, labels the identification of the firing of one's pain centres in the brain with feeling pain ‘a naive view,’ the refutation of which cannot much threaten any serious version of materialism. But in fact at least a dozen proponents of contemporary materialism have already hypothesized the identification of feeling pain with activation of a specific neural mechanism, although they picked the wrong mechanism, namely C-fibres. Just to take a recent example, James Cornman and Keith Lehrer, trying to get around the objection to the identity theory that the language of neural processes and the language of feeling pains belong to different linguistic categories, suggest that the materialist could devise a new term to refer to the same entity across categories: ‘fibain.’

They write,

Events have played a central role in a number of recent philosophical analyses. In general, there are two different sorts of arguments that might be offered in favour of an event analysis: first, it might be held that the constructions being analyzed contain certain nominals (expressions like “the sinking of the Lusitania,” or “Nixon's resignation“) which intuitively refer to events, and further that any satisfactory analysis must respect these intuitions; second, it might be argued that quite aside from our intuitions, the concept of an event — perhaps as a purely technical device — permits the solution of philosophical problems implicit in alternative non-event analyses (which typically take nominals as non-referring sentence transformations).

I wish to argue that both the above sorts of arguments fail. First, I argue that our intuitions about the reference on nominals are inconsistent, varying from context to context, so that the various sorts of event analyses cannot be talking about a single category of entities.

In a recent paper Lawrence Davis has argued that the difference between an arm raising and someone raising his arm is that in the latter case a volition causes the arm to rise. In this paper I will show that Davis's theory is faulty and that certain obvious ways of repairing his theory do not work.

Davis proposes the following as an account of Sam's raising his arm:

According to Davis the volition — Sam's willing to raise his arm — need not be interpreted psychologically. Volitions could be ghostly mental events, but they might not be. He leaves this open. He also leaves open the question of whether volitions are introspectable events. Davis allows that in some cases Sam's arm rising can be caused by a volition different from the volition to raise his arm. For example, Sam might will to step on a pedal.