The Philosophy of Physics. Physics versus Metaphysics

Transcription

1 The Philosophy of Physics Lecture One Physics versus Metaphysics Rob Trueman University of York

2 Preliminaries Physics versus Metaphysics Preliminaries What is Meta -physics? Metaphysics as Continuous with Physics Living with Physics

3 Preliminaries Course Structure Contact Hours hour lectures (Wednesday 09:00 10:30) hour seminars (Thursday 13:30 15:00) Weekly Office Hour (Tuesday 14:30 15:30) Procedural Requirements Attend lectures and seminars Complete all required reading Participate in seminar discussions (Please bring copies of seminar readings with you, as well as at least one study question in writing) Assessment 1 1,200 word essay, due 12 noon Monday Week 7, Autumn Term (Formative) 1 4,000 word essay, due Monday Week 1, Spring Term (Summative)

4 Preliminaries Readings Required weekly readings for seminars These can be found in your reading pack A comprehensive reading list can be found in the EARL list on the VLE page for this module It is important that you bring your reading pack to the seminar! A useful textbook: Sklar, L (1992) Philosophy of Physics (esp. chs 2 & 4) An accessibile introduction to the philosophy of space and time: Dainton, B (2010) Space and Time, 2nd edition (esp. chs 9 13 & 18 21) An excellent book on the philosophy of Quantum Mechanics: Albert, D (1992) Quantum Mechanics and Experience

5 What is Meta -physics? The Meaning of Metaphysics Meta = Beyond or After Metaphysics = Beyond / After Physics A very evocative name! But really, it s called that only because Aristotle thought that ontological philosophy should be taught after natural philosophy Still, this suggests that metaphysics can be separated from physics. Can it?

6 What is Meta -physics? The Questions of Metaphysics Metaphysics has traditionally been thought of as an investigation into the fundamental nature of reality What kinds of thing are there in the world? What are those things like? Historically, philosophers have found it tempting to think of this kind of investigation as being of a very different kind from the investigations of the natural sciences

7 What is Meta -physics? Aristotle s Presentation of Metaphysics There is a science which investigates being as being and the attributes which belong to this in virtue of its own nature. Now this is not the same as any of the so-called special sciences; for none of these others deals generally with being as being. They cut off a part of being and investigate the attributes of this part this is what the mathematical sciences for instance do.

8 What is Meta -physics? Aristotle s Presentation of Metaphysics Now since we are seeking the first principles and the highest causes, clearly there must be some thing to which these belong in virtue of its own nature. If then our predecessors who sought the elements of existing things were seeking these same principles, it is necessary that the elements must be elements of being not by accident but just because it is being. Therefore it is of being as being that we also must grasp the first causes. Aristotle, Metaphysics IV.1

9 What is Meta -physics? Metaphysics according to the OED 1.a. The branch of philosophy that deals with the first principles of things or reality, including questions about being, substance, time and space, causation, change, and identity (which are presupposed in the special sciences but do not belong to any one of them); theoretical philosophy as the ultimate science of being and knowing. Oxford English Dictionary

10 What is Meta -physics? Metaphysics according to the OED 1.a. The branch of philosophy that deals with the first principles of things or reality, including questions about being, substance, time and space, causation, change, and identity (which are presupposed in the special sciences but do not belong to any one of them); theoretical philosophy as the ultimate science of being and knowing. Oxford English Dictionary

11 What is Meta -physics? What exactly is the difference from physics? But there are branches of physics which are particularly concerned with questions about substance, time, space, causation... So what exactly is there left for metaphysics to do here?

12 What is Meta -physics? A Physicist Speaks We each exist for but a short time, and in that time explore but a small part of the whole universe. But humans are a curious species. We wonder, we seek answers. Living in this vast world that is by turns kind and cruel, and gazing at the immense heavens above, people have always asked a multitude of questions: How can we understand the world in which we find ourselves? How does the universe behave? What is the nature of reality? Where did all this come from? Did the universe need a creator? Most of us do not spend most of our time worrying about these questions, but almost all of us worry about them some of the time.

13 What is Meta -physics? A Physicist Speaks Traditionally these are questions for philosophy, but philosophy is dead. Philosophy has not kept up with modern developments in science, particularly physics. Scientists have become the bearers of the torch of discovery in our quest for knowledge. Hawking (2010), p. 13

14 What is Meta -physics? A Philosopher Speaks What reality is like is the business of scientists, in the broadest sense, painstakingly to surmise; and what there is, what is real, is part of that question. Quine (1960), p. 22

15 What is Meta -physics? Quinean Naturalism According to Quine, the traditional questions of metaphysics are really questions to be answered by plain old physics (and maybe the other empirical sciences) Questions of epistemology are questions of what is confirmed according to our best scientific standards of confirmation Quine s approach to metaphysics and epistemology is known as naturalism, and is pretty much orthodoxy in contemporary philosophy

16 Metaphysics as Continuous with Physics Physics versus Metaphysics Preliminaries What is Meta -physics? Metaphysics as Continuous with Physics Living with Physics

17 Metaphysics as Continuous with Physics First Philosophy Aristotle referred to his science of being qua being (i.e. metaphysics) as first philosophy Meditations on First Philosophy (in which the existence of God and the immortality of the soul are demonstrated) (Descartes)

18 Metaphysics as Continuous with Physics First Philosophy The Meditations is the archetypal work of modern metaphysics Descartes asks what there is; about the existence of god; about our existence and nature; about the existence and nature of material things Descartes tried to answer these questions before physics, in the sense that he professed all doubt of the so-called knowledge provided by science He took a foundationalist approach to knowledge: he was trying to build up our system of knowledge, starting at the bottom with absolutely certain foundations

19 Metaphysics as Continuous with Physics Quine s Confirmational Holism Quine rejected Descartes first philosophy Quine believed that a claim could only have empirical consequences when embedded in an entire theory; on their own, claims place no requirements on the world This Quinean doctrine is known as Confirmational Holism

20 Metaphysics as Continuous with Physics Quine s Confirmational Holism Our statements about the external world face the tribunal of sense experience not individually but only as a corporate body. Quine (1951), p. 41

21 Metaphysics as Continuous with Physics Abandoning First Philosophy Because a claim only places demands on the world when embedded in a wider theory (Confirmational Holism), we cannot abandon all our previous beliefs and still talk meaningfully about the world Instead we must work within the conceptual scheme provided for us by our current best scientific theories, without which we have nothing Quine uses Neurath s famous metaphor to present his holistic alternative to Descartes foundationalism

22 Metaphysics as Continuous with Physics Neurath s Boat Neurath has likened science to a boat which, if we are to rebuild it, we must rebuild plank by plank while staying afloat in it... The naturalistic philosopher begins his reasoning within the inherited world theory as a going concern. He tentatively believes all of it, but believes also that some unidentified portions are wrong. He tries to improve, clarify, and understand the system from within. He is a busy sailor adrift on Neurath s boat. Quine (1975), p. 72

23 Metaphysics as Continuous with Physics Quine s Naturalism the recognition that it is within science itself, and not in some prior philosophy, that reality is to be identified and described. Quine (1981), p. 21 The philosopher and the scientist are in the same boat. Quine (1960), p. 3

24 Metaphysics as Continuous with Physics Metaphysics as Continuous with Physics This has all led to the now widespread view that metaphysics is not a different kind of discipline from physics Metaphysics is continuous with physics Metaphysics is involved in the same overall enterprise as physics, and should interact with physics There can still be differences between physics and metaphysics, but they are just differences of degree Perhaps metaphysics is more abstract than physics? Perhaps metaphysics is more concerned with the interpretation of physical theories than physics itself is?

25 Metaphysics as Continuous with Physics But what does any of this Mean? What does it mean to say that metaphysics is continuous with physics? It had better mean more than that metaphysics and physics must mutually cohere Physics and literary theory had better cohere, since they are all trying to articulate truths and truths must be mutually coherent, but that hardly makes literary theory continuous with physics! Sometimes the point is meant to be that metaphysics should be informed by physics Fine, but if this is meant to vindicate the value of metaphysics, it had better also be that physics is influenced by metaphysics

26 Metaphysics as Continuous with Physics How much Metaphysics? There are some examples of metaphysical debates yielding scientific fruit Just wait until we read Einstein! But the vast run of metaphysics seems to be of no interest to the physicists Even if metaphysics is in some sense continuous with physics, most metaphysics is on the far end of that continuum At most, then, this sort of defence saves a very small branch of metaphysics Namely: philosophy of physics!

27 Metaphysics as Continuous with Physics The Interpretation of Physical Theories If you ask a physicist to explain, in plain English, what their physical theories actually mean, they are likely to speak a lot of nonsense If you ask a (good, well-informed) philosopher of physics what a given physical theory means, you are much more likely to get a good answer But we have not yet been told why this should matter Physicist get by with their unsatisfying explanations, and nonetheless carry on producing good physics Shut up and calculate! Does the formal language used by physicists need to be translated into ordinary English in order to be meaningful just as it is?

28 Living with Physics Physics versus Metaphysics Preliminaries What is Meta -physics? Metaphysics as Continuous with Physics Living with Physics

29 Living with Physics Sellars on the Manifest Image Sellars (1962) offered a very different picture of the relationship between science and philosophy The Manifest Image The world as it presents itself to us The Scientific Image The world as it is described by modern science These two images can be difficult to reconcile

30 Living with Physics Manifest Image

31 Living with Physics Scientific Image

32 Living with Physics The Images Collide The car of the manifest image is a solid, coloured object The cloud of particles of the scientific image is in no straightforward sense solid, and definitely has no colour So how can we identify the car with the particles? Questions like these become even harder when we take Quantum Mechanics into account! And they become harder still when we stop asking how cars can be identified with anything in the Scientific Image, and start asking about how people can be!!!

33 Living with Physics Just More Science? A natural thought is that it is philosophy s job to reconcile the Manifest and Scientific Images I think that there is something plausible here, but put like this there is a problem It is tempting to say that we really need science, not philosophy, to reconcile the images: If we want to know why a cloud of particles looks like a solid car to us, then we need to look at things like Quantum Mechanics, Optics and Neurobiology

34 Living with Physics Our Alienation from the Physical World Physical theories often suggest pictures about how the world is These world-pictures are often very deeply alienating for people who live lives like ours

35 Living with Physics Example 1: Determinism Newtonian mechanics is deterministic Given the total state of the world at one time, and all of the Newtonian laws governing the world, we can deduce the state of the world at any other time Everything you have ever done was determined by the state of the world long before you were born, and by the laws of physics So you did not really have any say in what you did You are not free

36 Living with Physics Example 2: Evolution Given the nearly universally accepted theory of evolution, humans evolved from lower apes, which evolved from lower primates, which evolved from... which evolved from a single celled life-form Humans are not apart from the animal kingdom, but are just at one of the extremities of the evolutionary tree Our cognitive capacities are not transcendental tools of pure reason, but evolutionarily condition tools for survival

37 Living with Physics Example 3: The Size of the Universe The observable universe stretches something like 14 billion lightyears in every direction It is filled with galaxies which are filled with stars which are surrounded by planets, and between all of that is vast, stretching nothingness We are stuck in an insignificant part of an insignificant galaxy Nothing we can do will ever make much of a difference on the universe as a whole So nothing we can do will ever really matter

38 Living with Physics A Practical Problem These are all deeply alienating pictures, in the sense that they make it hard to know what we should do, how we should live How should you feel about someone s behaviour if they are not free? How far should you trust your own reason if it was evolved for survival in a particular context? What should you bother doing if nothing matters? These theories thus throw up practical problems about how to live

39 Living with Physics A Role for Metaphysics At least one, legitimate role for metaphysics is to find a way of living with the physical theories that generate these pictures In some cases, this involves looking more closely at our everyday concepts, to show that they can still operate in the difficult world-pictures e.g. compatibalism about free will But in other cases, this involves looking more closely at how we interpret the physical theories themselves, to show that they do not force the unhappy world-pictures on us

40 Living with Physics Compared to Sellars There is an important difference between this role for metaphysics and the Sellarsian story about reconciling the Manifest and Scientific Images How to reconcile these Images is a theoretical puzzle: Both Images purport to describe the world That straightaway invites the thought that we should appeal to more science to solve the puzzle But on the alternative I have sketched, we are dealing with a practical, normative puzzle: How should you live your life, given that we live in a world which can be truly described by modern physics? This does seem distinctively philosophical, and that is precisely because it is a puzzle about what we should do Although I should mention that there are hints that this is exactly what Sellars had in mind!

41 Living with Physics References Hawking, S and Mlodinow, L (2010) The Grand Design (Bantam Books: London) Quine, WVO (1951) Two Dogmas of Empiricism, Philosophical Review 60: Revised and Reprinted in Quine (1961), pp (1960) Word and Object (MIT Press: Cambridge, MA) (1961) From a Logical Point of View, 2nd ed (Harvard University Press: Cambridge, MA) (1975) Five Milestones of Empiricism, reprinted in Quine (1981) pp (1981) Theories and Things (Harvard University Press: Cambridge, MA) Sellars, W. (1962) Philosophy and the Scientific Image of Man, reprinted in Sellars (1963) Empiricism and the Philosophy of Mind (Routledge: London)