Chapter 4 The Metaphysics of Time 4.1 Introduction For the most part, contemporary philosophy of time is governed by the distinction between Presentism and Eternalism. In understanding the nature of time, the choice seems to be between a moving present and a frozen history, laid out along the time-line. According to Presentism, the only concrete time that exists is the present. Everything that was past no longer exists and that which is in the future is yet to happen. The present moment keeps “flowing,” so that every instant is followed by a new instant in which part of the future becomes the present and the present becomes past. One frequently distinguishes between the past, present and future based on the types of action that are available. It is not possible to influence the past; actions take place only in the present. The future is pregnant with possibilities that might or might not be realized, depending on what we do in the present. Thus, Presentism is presupposed whenever one forms plans for the future or allows for the possibility that things could have been otherwise than they are. Commonsense intuition, linguistic habit, and practical reason render Presentism the natural position to take. But many philosophers believe that current scientific theories are in conflict with Presentism. According to the Eternalist view, or as it is sometimes called the block-universe view, everything in the past, present and future exists. Eternalism is based on an analogy between the spatial and temporal lines. It is uncontroversial to believe that everything that exists at present exists in three- dimensional space, even if one can only view existing things from a particular point in space. Similarly, the analogy goes, if one occupies a certain instant in time, one is only immediately aware of events that happen at that instant. But this limited aware- ness does not entail that past and future events do not exist. Some interpretations of the Special Theory of Relativity (STR), most notably that of Minkowski, suggest that space and time are abstracted from a more basic four-dimensional structure of spacetime. According to this approach time should be treated as if it were just another dimension for describing the manifold of events. If the temporal dimension is completely analogous to the spatial dimension, there is reason to believe that existence at a particular instant in time is analogous to existence at a particular point in space. Instants spread along the temporal dimension all exist, in analogy with points along a spatial line. O. Belkind, Physical Systems, Boston Studies in the Philosophy of Science 264, DOI 10.1007/978-94-007-2373-3_4, C  Springer Science+Business Media B.V. 2012 93