Commentary on time

Already we can begin to make our own asessment of some of the historical definitions that have been given in answer to the question ‘What is time?’

Plato – ‘The moving image of eternity’
Aristotle – ‘The number of movement in respect of ‘before’ and ‘after’
Immanuel Kant – ‘Transcendental … a pure form of sensible intuition … the form of inner sense … not an object . i.e. the dimension in which our own experiences are ordered’
John Locke – ‘Duration set out by measures’
Whitrow – ‘An aspect of the relationship between an observer and the universe: it co-exists with the universe’ Author of the book ‘What is Time’, 1972
John Smart -‘The dimension of change’ (Australian philos’er, quoted Encyclopaedia Brittanica)
Albert Einstein – ‘Past, present, and future exist simultaneously’ and in discussing Minkowski’s Space World interpretation of Relativity: ‘Since there exists in this four dimensional structure [space-time] no longer any sections which represent “now” objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence’(Relativity, 1952)
David Mellor -‘The dimension of causation’ (Cambridge University Philosopher of Time)

STATEMENT OF A PHILOSOPHY OF TIME
[Numbers in square brackets indicate chapter sections where statements are elaborated]

In the Epilogue to ‘A Brief History of the Philosophy of Time’ (2013) Adrian Bardon draws together the threads of contemporary thinking on time.

From the temporal idealists we have learned important lessons about both time and science itself. The only way we can understand the world outside our minds is through the mediation of our minds: we can never know if our representations of the world are accurate except through their explanatory power, simplicity, and application, not through a direct knowledge of nature itself. This does not cast us into a world of subjective uncertainty as we have every reason to believe that the mapping of our scientific explanations onto the world, our representations of the world, are becoming increasingly accurate. However, we can confidently expect that our particular way of understanding and experiencing the world will be a consequence of its biologically adaptive value to us as Homo sapiens. As conscious living organisms we are both deeply aware of and totally dependent on here and now. No doubt there is more to be gleaned about this from phenomenology and evolutionary psychology even if scientifically and philosophically we are persuaded by the early twentieth century philosophical and scientific work of McTaggart and Einstein that there is no special privileged moving now that we occupy.

A word in support of philosophy. We can quickly dismiss philosophy as being concerned with the unproductive niggling at unanswerable or meaningless questions. I hope that this series of articles has shown how philosophy, in fact, helps us to both identify the meaningless questions and locate the tough and abstract but answerable ones and to therefore make progress.

The ultimate constituents of the universe may be continuous, or discrete, or both – we do not know. It is conventional to segregate the universe into space, time and matter (mass-energy) but even a simple distinction like this is contentious. How can we unambiguously define each of these entities without reference to the others? We know from Relativity that space, time and matter interact in a way that makes their physical and theoretical isolation questionable. It has, for example, been postulated that matter is highly condensed space-time. In particular we learn from General Relativity that space and time are inextricably co-variantly woven together in the fabric of the universe, any measurement of one affecting that of the other. Nevertheless, since time is a separate dimension of space-time and because there are many occasions (especially in daily life) when the space-like component of space-time is irrelevant to discussion, it becomes meaningful to speak of time alone, although the underlying co-variant relationship with space should always be kept in mind.

Within the physical universe of space-time we cannot say with certainty whether space-time is substantival (absolute), that is, existing independently from other things as a substrate, or simply relational. This is a long-standing debate that is still not fully resolved. However, it is the view presented here that time is an objective part of the fabric of the universe and should be treated philosophically as an object, not as a relation. In other words time, contrary to much philosophical thinking – most notably that of McTaggart – is real. Perhaps the most persuasive demonstrations of its reality came after McTaggart’s paper of 1908 (which claimed the unreality of time) through Einstein’s predictions of time dilation. For example, after a period of time clocks on aircraft circling the Earth give different readings relative to clocks on Earth, and it is possible to calculate the precise difference according to Relativity theory. Such experiments are remarkable because they are counterintuitive and demonstrate the physical reality of time and its physical effects in situations that are independent of human percepts.

If we accept the physical reality of time, how does this bear on the complex semantic web of temporal ideas that are presented to us in everyday discourse? The future plays a vital role in all of our lives and yet few would claim that it is real. In claiming that it is unreal we are not denying that it is of vital, possibly critical, importance to our mental functioning, but that it has no reality beyond our minds in the external world. What are the subjective and objective components of time?

In everyday discourse (and some scientific discourse) it is extremely significant that the word time is used with several meanings. This bears strongly on philosophical discussion yet is not apparent in the literature.

The future is what has not yet happened, the past is what has happened, and the present is what is happening now. Nothing happens in the future or the past but we can subjectively anticipate, imagine or project into the future, and have memories and imaginative scenarios of the past. But all anticipation and memory is subjective and, most importantly, it occurs in the present. Since there is no objective past or future now, nothing can flow from future through present to past except in our minds: events just happen, they cannot literally move towards us from the future, except as calculated subjective projections. However, time does lapse in the present and this gives us the sensation of movement that we call the passage of time. Time lapse is real and objective but it is not spatial, and time is not a substance, therefore its description using spatial and substance words such as length, flow, distance and passage is metaphor. Temporal “passage” as literal spatial and substantial movement is illusory, but as lapse of time which feels like spatial movement it is objective and real, it is just that the spatial language so often used is inappropriate. Time lapses in the present and is temporal not spatial. All spatial talk of accretion and extension is similarly inappropriate, as is talk of things coming into, and going out of, existence. All this implies movement of events or things into and out of the past and future. There are simply changes in the present.

In summary, the present is real and consists of our subjective response, the specious present, to the objective now, which is time itself. The past and future are not objective constituents of the universe but subjective memory and anticipation. Therefore monadic temporal properties like pastness, presentness and futurity, and being one week past, 1 day future etc (A-properties) have no objective counterparts.

Objective, physical time is the now: what has been described as the knife-edge between what we call past and future, between indeterminacy and determinacy; the actuality between potentiality and unalterable necessity: it is different from the psychological now. The place of now in the universe will depend on its relativistic frame of reference but it is, nevertheless, an objective part of the physical world. There was a now at the Big Bang and a now as the universe and biological organisms evolved, and that cosmic now did not depend for its existence on the presence of human observers. The history of the universe, of the rock strata and the fossils they contain, and of the organisms that have evolved, bear witness to an objective now of the past.

We sense time always, but measure it using clocks of various kinds – instruments with isochronous intervals. The human psychological now (specious present) is not of a precise length but of a period suitable for our biological adaptation to the threats and needs of our environment. It is sufficiently short to make us concentrate when driving cars or playing table-tennis – occasions when our judgement of now can be critical. The psychological now is an adaptation to the objective now of the universe. When people in different countries tune in to a football match on television, the simultaneous now is not a common illusion or a mutual convention, it is a public and objective reality. The now of the universe is divisible to the finest precision of our most accurate clocks and finer still.

Time is not simply the temporal relations between events. The relations of earlier than, simultaneous with and later than do not account for duration, which we can both sense and measure.

Time is not space: it is not the movement of the hands, or the flashing of numbers on a clock (it is the temporal intervals they represent); it is not change (although we can hardly imagine time without change); it is not spatial length as represented by a line (although we can represent time with a line, time is not the line itself). Temporal length as represented by the aging of everything that is actual. Time moves in the sense that temporal distances can increase and decrease, but these are not spatial distances, and therefore the movement of time is not the same as the movement of a river. It therefore does not make sense to ask how fast time flows.

Since all the major aspects of time we have considered – becoming, duration are objective, they are therefore part of the empirical world and therefore essentially a matter for science (physics) rather than metaphysics, although philosophy can assist in clarifying concepts.

The solution to the problems of time cannot be semantic – it must be empirical.
[The description of time is largely an empirical matter.
What time actually is, and the role it plays in language] Time is an unspace-like dimension.

BIBLIOGRAPHY
History & general background
Callender,C. (ed.) 2011. The Oxford Handbook of the Philosophy of Time. Oxford University Press: Oxford

Causation
Trisel, B.A. (1999). The causal attainment theory of temporal passage. Sorites 10: 60-73.
*Tooley, M. (1997). Time, tense and causation. Clarendon Press, Oxford.

Four-dimensionalism (3D/4D)
*Prior, A. (1968). Changes in events and changes in things. In: Papers on time and tense. OUP, London. An account of tensed discourse in terms of modal logic.
Butterfield, J. (1984). Spatial and temporal parts. The Philosophical Quarterly 35: 32-44.
Heller, M. (1993). Varieties of four dimensionalism. Australasian Journal of Philosophy 71: 47-59.
Markosian, N. (1994). The 3D/4D controversy and non-present objects. Philosophical Papers 23: 243-249.
Mellor, D.H. The time of our lives. Royal Institute of Philosophy lecture, available on the web www.dar.cam.ac.uk/dhm11/TimeLives.html
Parsons, J. (2001). Must a four-dimensionalist believe in temporal parts? Post-final version, internet.
Sider, T.R. (1997). Four-dimensionalism. The Philosophical Review 106: 197-231.
Smart, J.J.C. (1963). Philosophy and scientific realism. Routledge and Kegan Paul, London.
Smart, J.J.C. Time In: Edwards, P. (ed). The encyclopaedia of philosophy. Collier-MacMillan, London.

Arrow of time
Price, H. (1996). Times arrow & Archimedes point: new directions in the physics of time. OUP, Oxford.
Coveny, P. & Highfield, R. (1990). The arrow of time. Fawcett Columbine, New York.

Relativity
*Hickenfuss, I. (1975). The existence of space and time. Clarendon Press, Oxford.
Smart, J.J.C. Spatializing time. In Gale (1967)
Edwards, P. (ed.) (1973). Problems of space and time. Collier-McMillan, London.

Absolute & relational time & substantivism
Rynasiewicz, R. (1996). Absolute versus relational space-time an outmoded debate? J. Philosophy 93: 279-306.
Shoemaker, S. (1969). Time without change. Journal of Philosophy 6: 363-381.
*Hoefer, C. (1998). Absolute vs relational space-time: for better or worse the debate goes on. British Journal of the Philosophy of Science 49:

Space and time
Taylor, R. (1955). Spatial and temporal analogies and the concept of identity. Journal of Philosophy 52:
*Stein, H. (1968). On Einstein-Minkowski space-time. The Journal of Philosophy 65: 5-23.

General
*Audi 103A911C (1999). Cambridge encyclopaedia of philosophy.
Bardon, A. 2013. A Brief History of the Philosophy of Time. Oxford University Press: Oxford
*Butterfield, J. (ed.) (2000). The arguments of time. OUP
*Craig, E. (ed) (1998). Routledge encyclopaedia of philosophy. Routledge
Gale, R.M. (1967). The philosophy of time. Macmillan Reissued 1978
*Gale, R.M. (1968). The language of time. Routledge & Kegan Paul,
Aveni, I. (1989). Empires of time. Basic Books, New York.
Davies, P. (1995). About time. Penguin, London.
Flood, R. & Lockwood, M. (eds)(1988). The nature of time. Basil Blackwell, Oxford.
Fraser, J.T. (ed.) (1968). The voices of time. Allen Lane The Penguin Press, London.
Hawking, S. (1997). A brief history of time. Bantam, Sydney.
LePoidevin, R. & McBeath, M. (eds) (1993). The philosophy of time. Oxford University Press.
Newton-Smith, W.H. (1980). The structure of time. Routledge & Kegan Paul, London.
Pendleton, R.L. (2000). Time and supervenience. Members.aol.com/pendletonz/time_supervenience.html.
Penrose, R. (1994). Shadows of the mind. OUP, Melbourne.
Poidevin & Macbeath (1993). The philosophy of time. OUP
Royal Observatory Greenwich information leaflets. www.rog.nmm.ac.uk
Smart, J.J.C. ( ).Encyclopaedia Britannica. Time.
Whitrow, G.J. (1961). The natural philosophy of time. Thomas Nelson, London.
Whitrow, G.J. (1972). What is time? Thames & Hudson, London.
Whitrow, G.J. (1989). Time in history. O.U.P., Oxford.
Wilson, C. (ed.) (1980). The book of time. Jacaranda Press, Milton.

Presentism
*Bigelow, J. (1996). Presentism and properties. In J. E. Tomberlin (ed.) Philosophical Perspectives 10, Metaphysics: 35-52. Blackwell, Cambridge Ma.
*Prior, A. (1967). Past, present and future. OUP
Chown, M. (2000). Backwards to the future. New Scientist 165(2224): 26-31.
Gale, R. (1969). Here and now. The Monist 53: 396-409.
Garson, J.W. (1969). Here and now. The Monist 53: 469-477.
Markosian, N. (2001->). A defense of presentism. Markosian web site.
*Oaklander, N. (1994). Bigelow, possible worlds … Analysis 54(4): 244
*Prior, A.N. (1959). Thank goodness that’s over. Philosophy 34: 12-17.
Seager, W. (?). The reality of now.
*Smith, Q. (1988). The phenomenology of A-time. Dialogos 52: 143-153.
Taylor, R. (1962). Fatalism. Philosophical Review 71: 56-66.
Williams, C. (1992). The phenomenology of B-time. Southern Journal of Philosophy 30: 123-137.

Becoming
* Prior, A.N. (1968) Changes in events and changes in things. In LePoidevin & McBeath.
Brooke Alan Trisel (1999). The causal attainment theory of temporal passage. Sorites 10: 60-73. Abby2tris@cs.com
Broad, C.D. (1938). Ostensible temporality. In Gale (1967).
Markosian, N. (1993). How fast does time pass? Philosophy and phenomenological Research 53: 829-844.
Markosian, N. (1992). On language and the passage of time. Phiosophical Studis 66: 1-26.
Markosian, N. (2001?). Review of: Semantics, tense and time. By Ludlow, P. Cambridge, MA.
*Mundle, C.W.K. (1966). Augustine’s pervasive error concerning time. Philosophy 41: 165-168.
Russell, B. (1915). On the experience of time. The Monist 25: 212-233.
Smart, J.J.C. (1949). The rivers of time. Mind 58: 483-494.
Williams, D.C. (1951). The myth of passage. Journal of Philosophy 48: 457-472.
Markosian, N. (1993). How fast does time pass? Philosophy and Phenomenological Research 53: 829-844.
*Smith, Q. (1987). Problems with the new tenseless theory of time. Philosophical Studies 52: 371-392.

McTaggart
Mellor, D. (1998). Real Time II. Routledge, New York.
Craig, W.L. (2001) McTaggart’ paradox and temporal solipsism. Aust. J Phil. (March)
McTaggart, J.M.E (1908). The unreality of time. Mind 18: 457-484.
Oaklander, L. N. (1993->). Time and change. Updated paper available on the web
*Oaklander, N. (2000). A & B time …..Journal of Philosophical Research ….
Parsons, J. (2001). A-theory for B-theorists. Josh Parsons Web Page.
*Dyke, H. (2001). Tensed meaning: a tenseless account. J. Philosophical Research
*Dyke, H. (2001). Tokens, dates and tenseless truth conditions. Synthese
*Dyke, H. (2002). Thank goodness that’s over – the evolutionary story. Ratio
*Callender, C. (ed.) (2002). Time, reality and experience. CUP
The last three minutes.

Possibilism – time and modality
Bigelow, J. (1991). Worlds enough for time. Noûs 25: 1-19.
Menzel, C. (2000). Three types of possibilism. Stanford Encyclopaedia. Internet.
Lewis, D.
*Dowe, P. (2000?) Fiction and time travel. Internet.
*Dowe, P. (2000). The case for time travel. Philosophy 75: 441-451.
*Keller, S. & Nelson, M. (2001). Why presentists should believe in time travel. Australasian Journal of Philosophy
Lewis, D. K. (1986). On the plurality of worlds. Blackwell, Oxford.
*Lucas, J.R. (1989). The future. Blackwell, Oxford.

Glossary
Duration – A temporal interval
Endurantism – the view that material objects persist as three-dimensional objects wholly present at every moment of their existence
Eternalism – the past, present and future exist equally
Now – the indeterminacy of the future (unknown, subjective) giving way to the determinacy of the past (known, objective): the coming into being of determinate reality (objective). Note that this definition is given in the present tense and also that it is not ‘the moment when’ now occurs. Now is time itself. Now is the only semantic element of the semantic taxonomy (excluding T(a) and T(r)) that does not exist in time T(ud)
Perdurantists think that objects have both spatial and temporal parts, while endurantists think that they only have spatial parts. From an endurantist point of view, however, it is difficult even to say what temporal parts are supposed to be. Your temporal parts are parts of you which lie in the past or in the future>
Present – the current state of affairs or now as perceived and acted upon by humans
Past-presentism – The past and present exist but not the future
Presentism – only the present exists
Succession – The sequence of things (times and events;(facts, people or objects) which may be either earlier than, simultaneous with or later than the present (now), or one-another