A and B Theories of Time, and the Kalam Cosmological Argument

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Image Credit: Masco Digital Photography.

Philosophers identify two broad and competing views on the nature of time: A-theory and B-theory. Whichever theory one endorses, it will shape how one views the world. In theology and the philosophy of religion, how one sees the nature of time will also influence how he or she sees God.

These concepts were initially proposed by the idealist philosopher John McTaggart in his 1908 paper The Unreality of Time. McTaggart saw A-theory as contradictory although he still believed that A-properties (such as the past) are essential to the human conception of time. McTaggart deduced by way of conclusion that the human concept of time is therefore incoherent (this is referred to as “McTaggart’s Paradox”), and his ideas have lead to a considerable development within the philosophy of time.

The primary difference between the two theories concerns whether or not time is tensed (A-theory) or tenseless (B-theory). A-theory is tensed in the sense that if one were to say that “I am in the middle of training,” the statement depends on the temporal perspective, namely, the present. On this view there is a real difference between past, present, and future in that these are real objective features of reality. Right now the present is all that exists, a view known as presentism, whereas the past no longer exists, and the future is still yet to exist and is based on potentiality (it is not fixed and determinate like the past). Philosopher Ted Sider explains that “Presentism is the doctrine that only the present is real” (1). Temporal becoming, as it is called, is a primary belief asserting that things and events come into being and go out of being. For example, a past historical event such as Caesar crossing the Rubicon with an army has already occurred and receded into the past, and therefore no longer exists. The past and future exist subjectively (the individual remembers the past and predicts the future) whereas only the present exists objectively outside of the human mind. Alhough B-theory has a large number of advocates among physicists and philosophers, A-theory seems both prima facie justified and intuitively obvious.

B-theory (also known as a tenseless or static theory) says says there isn’t a difference between past, present, and future, and that they are all equally real (this is referred to as eternalism). So, for example, something that has occurred in the ‘past’ is still real, and hasn’t simply just gone out of existence. Both Plato and tomorrow’s events, for example, exist right now even though they are not in the same space-time vicinity, and despite the fact that they cannot be viewed or interacted with (2). The future is thus just as real as the present and the past. According to the B-theorist, what one perceives of a continuum such as past, present, and future is ultimately an illusion of human consciousness. Things on A-theory such as temporal becoming do not exist because events do not come in and out of existence. There is no flow of time or the passing of time. Philosopher William Lane Craig is critical of B-theory because it does not seem to accord,

“with our experience of time. We all experience the present-ness of time and I see absolutely no reason to think that this is a gigantic delusion that has been foisted upon us. I see no reason to think this is illusory” (3).

However, many reject A-theory and presentism in favor of eternalism and argue that the former is in conflict with Einstein’s special and general theory of relativity. B-theory, however, corresponds with it. Philosopher Dean Rickle says that “the consensus among philosophers seems to be that special and general relativity are incompatible with presentism” (4). It is argued that the theory of special and general relativity show convincingly that there is no such thing as absolute simultaneity, an important requirement for A-theory. The relativity of simultaneity says that viewers in different frames of reference can potentially have different perceptions of events and whether or not those events occurred at the same time or at different times.

In the philosophy of religion this is of some implication. A popular argument for the existence of God largely popularized by William Lane Craig is known as the Kalam cosmological argument. It argues that whatever begins to exist has a cause, and that because the universe itself begun to exist it must too have a cause. Some have argued that B-theory is a challenge to the premises of the argument. For example, given that B-theory says that time is purely subjective on the part of an individual, there is no “now,” or temporal becoming. If so, then how could the universe come into being; Craig explains,

“On a B-Theory of time the universe does not in fact come into being or become actual at the Big Bang; it just exists tenselessly as a four-dimensional space-time block that is finitely extended in the earlier than direction. If time is tenseless, then the universe never really comes into being, and, therefore, the quest for a cause of its coming into being is misconceived” (5).

The second premise to the argument (P2: the universe begun to exist) would be undermined. Thus, it is not difficult to see that should the universe not have come into being then it is unwarranted to imply or argue that it owes its existence to a creator. However, Craig maintains the truth of A-theory, while others reject the notion that the Kalam cosmological argument needs to involve a commitment to A-theory (6).


1. Craig, W. 2007. God and Time. Available.

2. Markosian, N. 2002. Time. Available.

3. Craig, W. 2007. Ibid.

4. Rickles, D. 2007. Symmetry, Structure, and Spacetime. p. 158.

5. Craig, W. 2012. The Blackwell Companion to Natural Theology. p 183-184.

6. Waters, B. 2015. Toward a new kalām cosmological argument. Arts and Humanities, 2 (1): p. 1–8.



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