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B-theory of time

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Title: B-theory of time  
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B-theory of time

The B-theory of time is a term, given to one of two positions taken by theorists, in the philosophy of time. The labels, A-theory and B-theory, are derived from the analysis of time and change developed by Cambridge philosopher J. M. E. McTaggart in 'The Unreality of Time' (1908), in which events are ordered via a tensed A-series or a tenseless B-series. A-series is closely related to presentism while B-series is closely related to eternalism.


  • Description 1
  • Notes 2
  • References 3
  • External links 4


Events (or 'times'), McTaggart observed, may be characterized in two distinct, but related, ways. On the one hand they can be characterized as past, present or future, normally indicated in natural languages such as English by the verbal inflection of tenses or auxiliary adverbial modifiers. Alternatively events may be described as earlier than, simultaneous with, or later than others. Philosophers are divided as to whether the tensed or tenseless mode of expressing temporal fact is fundamental. Those who (like Arthur Prior[1]) take the tensed notions associated with the past, present and future to be the irreducible foundations of temporality and our conceptions of temporal fact, are called A-theorists (similar to presentists). A-theorists deny that past, present and future are equally real, and maintain that the future is not fixed and determinate like the past. Those who wish to eliminate all talk of past, present and future in favour of a tenseless ordering of events are called B-theorists. B-theorists (such as D.H. Mellor[2] and J.J.C. Smart[3]) believe that the past, the present, and the future are equally real.

The past, the present, and the future feature very differently in deliberation and reflection. We remember the past and anticipate the future, for example, but not vice versa. B-theorists maintain that the fact that we know much less about the future simply reflects an epistemological difference between the future and the past: the future is no less real than the past; we just know less about it (Mellor 1998). A view was held, for example by Quine and Putnam, that physical theories such as special relativity and latterly Quantum mechanics provide the B-theory with compelling support.[4][5]

A-theorists on the other hand believe that a satisfactory account of time must acknowledge a fundamental metaphysical difference between past, present and future (Prior 2003). The difference between A-theorists and B-theorists is often described as a dispute about temporal passage or 'becoming' and 'progressing'. B-theorists argue that this notion is purely psychological and not epistemological, and embodies serious confusion about time, while many A-theorists argue that in rejecting temporal 'becoming', B-theorists reject time's most vital and distinctive characteristic. It is common (though not universal) to identify A-theorists' views with belief in temporal passage.

The debate between A-theorists and B-theorists is a continuation of a metaphysical dispute reaching back to the ancient Greek philosophers Heraclitus and Parmenides. Parmenides thought that reality is timeless and unchanging. Heraclitus, in contrast, believed that the world is a process of ceaseless change, flux and decay. Reality for Heraclitus is dynamic and ephemeral. Indeed the world is so fleeting, according to Heraclitus, that it is impossible to step twice into the same river. The metaphysical issues that continue to divide A-theorists and B-theorists concern the reality of the past, the reality of the future, and the ontological status of the present.

The B-theory of time has support from physics. In special relativity, the relativity of simultaneity implies there is not a unique present. Many of special relativity's counter-intuitive predictions such as length contraction and time dilation are a result of this. Experimental confirmation of both effects include the time dilation of moving particles and shifts in the atomic clocks of satellites in orbit. Relativity of simultaneity implies a block universe where the present for different observers is a time slice of the four dimensional universe. Thus it is also common (though not universal) for B-theorists to be four-dimensionalists, that is, to believe that objects are extended in time as well as in space and therefore have temporal as well as spatial parts. This is sometimes called a time-slice ontology (Clark, 1978). This theory of time is depicted in the movie Interstellar. The physics of Interstellar was based on the work of renowned physicist Kip Thorne.[6] Astronaut Cooper enters a black hole that is a closed time-like curve, which allows him to transmit information back to a time in his perceived past. According to the B-theory of time, this is consistent and does not induce a paradox.

The B-theory of time is also criticised by philosopher and theologian William Lane Craig due to time becoming an entirely subjective phenomenon, and hence not an objective feature of reality. In the absence of minds, Craig objects, every temporal moment and event simply exists tenselessly; there are no tensed facts; no past, present, or future; nothing comes into existence or happens except in the tenseless sense of existing at certain appointed stations as opposed to others. If the mental phenomenon of temporal becoming is an objective feature of reality, this amounts to a denial of the B-theory of time.[7] If the B-theorist bites the bullet, stating that there is no temporal becoming of mental states, then this flies in the face of experience. In support of this view, Craig cites early 20th century astronomer and physicist Sir Arthur Eddington who stated: "We have direct insight into 'becoming' which sweeps aside all symbolic knowledge as on an inferior plane. If I grasp the notion of existence because I myself exist, I grasp the notion of becoming because I myself become. It is the innermost Ego of all that is and becomes."[8][9] However, one might still claim that the passing of time – which is the change in "present" moment – can be slower or faster, which likely depends on the amount of man's consciousness inserted between two moments.

William Lane Craig also insists that the B-Theory suffers the same incoherence as all theories that time is illusory, namely, that an illusion or appearance of becoming involves becoming, so that becoming cannot be mere illusion or appearance. In his view, the Buddhist can consistently deny the reality of the physical world, since the illusion of physicality does not entail physicality, but this is not the case with temporal becoming. As an example, Craig cites early 20th century philosopher John Laird who wrote: "Take the supposed illusion of change. This must mean that something, X, appears to change when in fact it does not change at all. That may be true about X; but how could the illusion occur unless there were change somewhere? If there is no change in X, there must be a change in the deluded mind that contemplates X. The illusion of change is actually a changing illusion. Thus the illusion of change implies the reality of some change. Change, therefore, is invincible in its stubbornness; for no one can deny the appearance of change."[10][11]


  1. ^ (French)
  2. ^ "Philosophy Cambridge Mellor Time Tense". Retrieved 2014-03-03. 
  3. ^ "Google Drive Viewer". Retrieved 2014-03-03. 
  4. ^ "Time-slices of particular continuants as basic individuals: An impossible ontology - Springer". 1978-05-01. Retrieved 2014-03-03. 
  5. ^ "Google Drive Viewer". Retrieved 2014-03-03. 
  6. ^ "New 'Interstellar' Trailer Goes Deep; Plus Kip Thorne Featurette". /Film. October 1, 2014. Retrieved October 5, 2014. 
  7. ^ Craig, William Lane (2000). The Tenseless Theory of Time: A Critical Examination. Dordrecht [u.a.]: Kluwer Acad. Publ.  
  8. ^ Eddington, Arthur (1928). Nature of the Physical World: Gifford Lectures. Cambridge, UK: Cambridge University Press. p. 7.  
  9. ^ Craig, William Lane (2000). The Tenseless Theory of Time: A Critical Examination. Dordrecht [u.a.]: Kluwer Acad. Publ. p. 171.  
  10. ^ Laird, John (1940). Theism and Cosmology, Being the First Series of a Course of Gifford Lectures on the General Subject of Metaphysics and Theism Given in the University of Glasgow in 1939. London, UK: George Allen and Unwin Ltd. p. 145.  
  11. ^ Craig, William Lane (2000). The Tenseless Theory of Time: A Critical Examination. Dordrecht [u.a.]: Kluwer Acad. Publ. p. 176.  


  • Clark, M. (1978) 'Time-slices of particular continuants as basic individuals: An impossible ontology'. Philosophical Studies 33, 403--408.
  • Davies, Paul (1980) Other Worlds. Harmondsworth: Penguin.
  • McTaggart, J.M.E. (1908) 'The Unreality of Time', Mind 17: 457-73.
  • McTaggart, J.M.E. (1927) The Nature of Existence, Vol II. Cambridge: Cambridge University Press.
  • Mellor, D.H. (1998) Real Time II. London: Routledge.
  • Prior, A.N. (2003) Papers on Time and Tense. New Edition by Per Hasle, Peter Øhrstrøm, Torben Braüner & Jack Copeland. Oxford: Clarendon.
  • Putnam, H. (2005) 'A Philosopher Looks at Quantum Mechanics Again', British Journal for the Philosophy of Science, 56, pp 615 - 634.
  • Quine, W. V. O. (1960) Word and Object, Cambridge, MA: M.I.T. Press.

External links

  • Markosian, Ned, 2002, "Time", Stanford Encyclopedia of Philosophy
  • Arthur Prior, Stanford Encyclopedia of Philosophy
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