B-theory of time

The B-theory of time is the name given to one of two positions regarding philosophy of time. B-theorists argue that the flow of time is an illusion, that the past, present and future are equally real, and that time is tenseless. This would mean that temporal becoming is not an objective feature of reality. The B-theory of time is the name given to one of two positions regarding philosophy of time. B-theorists argue that the flow of time is an illusion, that the past, present and future are equally real, and that time is tenseless. This would mean that temporal becoming is not an objective feature of reality. B-theory is often drawn upon in theoretical physics, and in theories such as eternalism. The labels, A-theory and B-theory, first coined by Richard Gale in 1966, 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. It is popularly assumed that the A theory represents time like an A-series, while the B theory represents time like a B-series. The terms A and B theory are sometimes used as synonyms to the terms presentism and eternalism, but arguably presentism does not represent time being like an A-series since it denies that there is a future and past in which events can be located. 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. Some philosophers have criticised hybrid theories, where one holds a tenseless view of time, but asserts that the present has special properties, as falling foul of McTaggart's paradox. For a thorough discussion of McTaggart's paradox, see R. D. Ingthorsson (2016). 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 or flux. 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 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. 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. Another way to characterise the distinction revolves around what is known as the principle of temporal parity, the thesis that contrary to what appears to be the case, all times really exist in parity. The A-theory (and especially presentism) denies that all times exist in parity, while the B-theory insists all times exist in parity. B-theorists such as D. H. Mellor and J. J. C. Smart wish to eliminate all talk of past, present and future in favour of a tenseless ordering of events, believing the past, present, and future to be equally real, opposing the idea that they are irreducible foundations of temporality. B-theorists also argue that the past, present, and future feature very differently in deliberation and reflection. For example, we remember the past and anticipate the future, 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. The B-theory of time has received support from the physics community. This is likely due to its compatibility with physics and the fact that many theories such as special relativity, the ADD model, and brane cosmology, point to a theory of time similar to B-theory. In special relativity, the relativity of simultaneity shows that there's no unique present, and that each point in the universe can have a different set of events that are in its present moment.