There is an ancient and ambiguous philosophical doctrine that perception is passive. This can mean that the mind contributes nothing to the content of our sensory experience: its power of perception is a mere receptivity. In this sense the principle has often been questioned, and is indeed doubtful on empirical grounds, given one reasonable interpretation of what it would be for the mind to make such a contribution.

Among A. J. Ayer's many influential contributions to philosophy are the accounts of the nature of metaphysics which he propounded at various stages of his philosophical development. Whereas his early position is a clear version of the antimetaphysical attitude of the Viennese circle and, more generally, of logical positivism, his later position is, as he generously emphasized, in some crucial respects indebted to Peirce's pragmatism and to Ramsey's analysis of the structure of theories. His later views on the nature of metaphysics are contained in his book Central Questions of Philosophy and in his reply to my criticisms in a Festschrift, published on the occasion of his retirement from the Wykeham Chair of Philosophy at Oxford University (Macdonald, 1979). Although in this reply he describes his later account of metaphysics as ‘much too perfunctory’, it does constitute an important attempt at answering one of the central questions of philosophy.

Unlike topics such as criminal responsibility, dangerousness has only recently begun to interest philosophically minded penologists. The most likely explanation is that until the middle of this century the periods for which people who had done serious harm to others were incarcerated in the UK so long that when they were released their age or condition or circumstances made them unlikely to repeat their crimes. It was only when pressure of resources—in plain terms overcrowded prisons and mental hospitals—forced the shortening of these periods that it became politically necessary to worry about the possible dangerousness of really substantial numbers of prisoners and patients who became eligible for release. The problem was not entirely new. A few lifers, for example, had been set free each year, under licences which lasted for the rest of their lives; and the Special Hospitals which housed the violent insane had discharged carefully selected inmates, also under supervision. But by the late 1960s the introduction of parole, the Mental Health Act and the abolition of capital punishment had greatly increased the number of cases in which the problem of dangerousness had to be faced, and difficult decisions had to be taken.

The theme of this paper is a philosophical theory of communication; more specifically, a theory about the understanding of language. It is an old theory, whose classical exponent was John Locke, and in the form that Locke expounded it the theory is now generally rejected by philosophers. But it is far from being a mere museum piece. The view about language that Locke put forward was a plausible one, and it has continued to be put forward in various forms. My main concern here is with a very recent version of the theory, contained in a book published early in 1975; however, it will be helpful to begin with a brief account of Locke's version. This is not only classical, but is also simple and clear, and as such it may serve as a useful stepping-stone towards an understanding of the more modern version.

Heidegger says concerning the question of the possibility of a proof of the existence of an external world that ‘the “scandal of philosophy” (Kant's words) is not that this proof has yet to be given, but that such proofs are expected and attempted again and again’. Heidegger thinks this because our being (Dasein) is in the world, and this is something which Descartes for one failed to appreciate. I am not concerned here to answer the question whether Heidegger's own views on these matters will do, though I think that they will not. Indeed they might well be said to beg the question at issue, in that Heidegger starts from the presumption that we are actually in the world, even if we are not in it in the way in which the tree in the garden is (and does not this last point make a great difference to the situation?). Another way of reacting to Heidegger would be to say that he does not treat the fact and force of scepticism seriously enough when he makes that presumption. After all, it is possible for us to raise sceptical doubts about the existence of a world apart from ourselves, while it is not possible for the tree in the garden to act similarly. Hence, even if we make the presumption that we are in the world, as Heidegger insists, we are in it in a way that leaves untouched the possibility of sceptical doubts about what that world and our being in it are like. It might, logically, be the case, for example, that the world consists of just me and that my being in the world is no more than for me just to exist. In other words, my being in the world does not directly entail that there exists a world apart from me.

Sartre presented ‘Existentialism and Humanism’ to a popular audience in Paris late in 1945. As he implies in the discussion which is appended to the text of the lecture (pp. 57–58), he was here simplifying his views so as to make them intelligible to a wide audience. In this he succeeded only too well; the lecture has become exceedingly well known and has been regarded as a definitive presentation not only of Sartre's philosophy at the time, but also of ‘existentialism’. One thing I hope to show in this essay is that this is not a sensible view to take; Sartre's text requires a good deal of interpretation and qualification in the light of his other writings of the period, and what emerges is a position which is uniquely his own. One way in which this can be seen is by considering Heidegger's ‘Letter on Humanism’ of 1947 which is a response to Sartre's lecture and is, indeed, Heidegger's only direct response to Sartre's work. In the lecture Sartre had associated Heidegger with himself as an ‘existential atheist’ (p. 26), but in his letter Heidegger emphatically dissociates himself both from atheism and from existentialism as characterized by Sartre, and goes on to criticize the position advanced by Sartre in the lecture. Yet despite the popular exaggeration of the significance of Sartre's lecture, it is certainly worth studying; for not only is it short and accessible, though in some respects misleading, it is also one of Sartre's few indications of the positive ethical theory which so many of his writings require but do not supply.

My aim in this paper is to consider the suggestion, made in an unpublished paper by Peter Hobson, a psychoanalytic colleague, that psychoanalysis is a form of life. Hobson is impressed by the peculiarity of psychoanalytic thinking, by its specialness, by the fact that its concepts are embedded in a system of practices and beliefs such that an outsider to all this may be unable to understand what the analyst says, whether to his patient or to another analyst. Hobson uses Wittgenstein's notion of a form of life to refer to this system of practices and beliefs, but he does not criticize or examine the notion itself.

A person's values are what that person regards as or thinks important; a society's values are what that society regards as important. A society's values are expressed in laws and legislatively enacted policies, in its mores, social habits, and positive morality. Any body's values—an individual person's or a society's—are subject to change, and in our time especially. An individual manifests his or her values in expressions of approval or disapproval, of admiration or disdain, by seeking or avoidance behaviour, and by his or her characteristic activities. What one values one seeks for or tries to maintain. Sometimes attaining it leads to unexpected enlightenment—that isn't what one wanted after all. But a person's values are discovered most significantly in a reflective way by becoming aware of what one is willing to give up to attain or maintain one's values. This is the price one is willing to pay for it, and values are occasionally, and in the money and stock markets always, expressed in terms of price. This can be significant or it can be misleading; it depends on how it is interpreted. Not everything has a monetary equivalent, despite the attempts of the law to provide recovery for damages in monetary terms, and despite the cynical maxim, ‘Everyone has his price’.

My topic may seem a bizarre mixture of epistemology and value theory; and perhaps it is best to acknowledge this oddity at once. I should also, perhaps, confess that such a mixture has always seemed something to aspire to. Any philosopher who has made it seem that feeling strongly about something, valuing it highly, is an inevitable consequence of the nature of human understanding, that from the facts of knowledge or perception one can derive the inescapable facts of emotion or desire, any such philosopher has always deeply appealed to me. I am therefore a confessed perpetrator of the naturalistic fallacy. Indeed I go further, and say that I love the fallacy. So Spinoza, Hume (however much people say that he first discovered naturalism to be fallacious) and Sartre all seem to me to be real philosophers, on the grounds that for them this connexion between knowing and wanting seemed inevitable. My aim is to illustrate this kind of connexion by suggesting that the human imagination is such that we ought to value it and respect it more highly than anything else; and that therefore, if it can be educated and improved, it is to this education that we should give priority, if we are concerned with education at all. It may seem on the face of it absurd to say that we ought to value any particular human faculty or capacity. It may be thought that this is not the kind of object or evaluation with which at any rate philosophers should be concerned. But the fact is, of course, that we do value very highly indeed all kinds of capacities that we have, such as sight, and hearing and understanding. And being unashamedly naturalistic, I have no hesitation in saying not only that we do value them, but that we ought to; they are, in every sense, valuable.

People value highly the digital technologies that are so pervasive in everyday life and work, certainly as measured by economists. Yet there are also evident harms associated with them, including the likelihood that they are affecting political discourse and choices. The features of digital markets mean they tend toward monopoly, so great economic and political power lies in the hands of a small number of giant companies. While tougher regulation may be one way to tackle the harms they create, it does not get at the structural problem, which is their advertising-driven business model. The hunt for people's attention drives algorithmic promotion of viral content to get ever-more clicks. An alternative policy intervention to reclaim public space would be to create a public service competitor that could drive competition along other dimensions. Online space must be reclaimed as a public space from the privately-owned US and Chinese digital giants.

I shall start by considering the apparently paradoxical doctrines that Wittgenstein put forward about knowledge: they show how the concept of knowledge is, as he says, ‘specialized’. This is not, as I shall show, a very important issue in itself, but it leads on to other points, of more interest: how it comes about, for example, that ‘not all corrections of our beliefs are on the same level’. I shall then discuss the idea that we inherit a certain picture of the world that forms the background of our experiments and researches. This idea, which is not of course unique to Wittgenstein, is, however, developed with many fresh insights. I end with some discussion of Wittgenstein's reported views on religious belief, which should not, in my opinion, be regarded as part of his contribution to philosophy, the interest of them being, perhaps, more biographical than philosophical.

My title is in a way misleading, for I want to show that there is a number of concepts of heaven. I want to explore these in the first part of this lecture. In the second part I shall comment on most ofthem, to see which, ifany, seem to be viable.

There are various ways in which a person's freedom of action may be diminished or restricted. Instead of acting, he may be acted upon; or he may be unable to help doing what he does. He may suffer from some disability, have a duty imposed on him or do something because he is obliged to do it. In this essay, I wish to examine the notion of being obliged to do something. I shall investigate the differences between ‘being obliged by A to do X’ and ‘being obliged to A for X’; between ‘being obliged to do X’ and ‘having (or being under) an obligation to do X’; between being physically obliged and being morally, legally and logically obliged; and between saying ‘X is something I am obliged to do’, ‘X is something I choose to do’ and ‘X is something I ought to do’.

There are many people who think that deconstruction has run its course, has had its day, and that it is now time to return to the important business of philosophy, or perhaps to serious ethical, social and political questions. Derrida's work, it is said, leads nowhere but a sterile philosophy of difference that in its de-politicized, de-historicized abstractness is a form of conservatism little better than the kinds of identity thinking to which it seems to be so radically opposed. In short, we must go ‘beyond’ deconstruction.

I come to praise contemporary French philosophy not to bury it. My aim is not to hail the appearance in France of a native brand of analytic philosophy—in itself an important event in the last decade—but to describe the indirect and selective importation of certain Anglo-Saxon concepts by French philosophers whose practice is far from analytic; and also to describe the resultant misunderstanding. In this paper I shall analyse the use of pragmatic concepts—and of the concept ‘pragmatics’—in the recent work by Deleuze and Guattari, Mille Plateaux, and I shall try to show that these concepts are the object of a creative misunderstanding, of a misprision.

In purporting to explain the occurrence of some event or process we cite the causal factors which, we assert, brought it about or keeps it in being. The explanation is a true one if those factors did indeed bring it about or keep it in being. In discussing explanation I shall henceforward (unless I state otherwise) concern myself only with true explanations. I believe that there are two distinct kinds of way in which causal factors operate in the world, two distinct kinds of causality, and so two distinct kinds of explanation. For historical reasons, I shall call these kinds of causality and explanations ‘scientific’ and ‘personal’; but I do not imply that there is anything unscientific in a wide sense in invoking personal explanation.

I am honoured and pleased to address you this evening on the life and work of an extraordinary American thinker, Charles Sanders Peirce. Although Peirce is perhaps most often remembered as the father of the philosophical movement known as pragmatism, I would like to impress upon you that he was also, and perhaps, especially, a logician, a working scientist and a mathematician. During his life time Peirce most often referred to himself, and was referred to by his colleagues, as a logician. Furthermore, Peirce spent thirty years actively engaged in scientific research for the US Coast Survey. The National Archives in Washington, DC, holds some five thousand pages of Peirce's reports on this work. Finally, the four volumes of Peirce's mathematical papers edited by Professor Carolyn Eisele eloquently testify to his contributions to that field as well.

‘Relativists' and ‘absolutists' about truth often see their own camp as promoting virtues, such as open-mindedness and intellectual humility, and see the opposing camp as fostering vices, like closed-mindedness and arrogance. Relativism is accused of fostering these vices because it entails that each person’s beliefs are automatically right for the person who holds them. How can we be humble or open-minded if we cannot concede that we might be wrong? Absolutism is accused of fostering these vices because the view is seen as entailing certainty. This also seems to preclude us from conceding that we could be wrong. However, no relativist defends the Protagorean version of relativism that entails infallibilism. And no absolutist posits infallible certainty. Fallibilism really is a precondition of various virtues, but both camps take themselves to be defending fallibilist positions against opponents who they take to be committed to infallibilism. Philosophers may inadvertently end up promoting precisely the sort of infallibilism they oppose by creating a false dichotomy and caricaturing the opposing camp. This underscores the importance of interpretive charity in both academic and public debate.

The mass media of communications have often been charged with making our life more vulgar than need be. The assumption which underlies what I have to say is that the influence of unique artistic sensitivities on society has also been increased by the mass media of communications. This is good news and I am aware of the risk I am courting when I attach importance to a promising kind of social change: the academic respectability of pursuing optimistic lines of thought is strictly limited in sociological circles.

I am very much honoured to have been asked to make the closing speech at this Conference. Since this is the first time for over fifty years that a philosophical congress of this scope has been held in England, I hope that you will think it suitable for me to devote my lecture to the revival of the empiricist tradition in British philosophy during this century. I shall begin by examining the contribution of the Cambridge philosopher G. E. Moore. Though he first owed his fame to his book Principia Ethica (Moore, 1903) regarded as a work of genius by the Cambridge Apostles and their associates in Bloomsbury, who did not venture to question Moore's mistaken view of ‘good’ as an unanalysable non-natural quality, his reputation now chiefly rests on his subsequent defence of common sense.