Eternalism (philosophy of time)

Eternalism is a philosophical approach to the ontological nature of time, which takes the view that all points in time are equally real, as opposed to the presentist idea that only the present is real, and the growing block universe theory of time in which past and present are real while the future is not. Eternalism is the view that each spacetime moment exists in and of itself. Modern advocates often take inspiration from the way time is modeled as a dimension in the theory of relativity, giving time a similar ontology to that of space (although the basic idea dates back at least to McTaggart's B-Theory of time, first published in The Unreality of Time in 1908, only three years after the first paper on relativity). This would mean that time is just another dimension, that future events are "already there", and that there is no objective flow of time. It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time.

Conventionally, time is divided into three distinct regions; the "past", the "present", and the "future". Using that representational model, the past is generally seen as being immutably fixed, and the future as undefined. As time passes, the moment that was once the present becomes part of the past; and part of the future, in turn, becomes the new present. In this way time is said to pass, with a distinct present moment "moving" forward into the future and leaving the past behind.

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