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#751 Is Spacetime Real?

September 26, 2021
Q

Is spacetime an actual physical entity, or is it just an a priori frame work we use to perceive the world. If it isn’t a real physical entity how can it have properties like curvature or expansion

Tariq

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Dr. craig’s response


A

I do not think that spacetime is an actual physical reality, Tariq, since it implies a tenseless theory of time according to which there is no objective difference between past, present, and future and temporal becoming is just a subjective illusion. In my books The Tensed Theory of Time and The Tenseless Theory of Time, as well as in my popularization Time and Eternity, I lay out the following case for a tensed theory of time over a tenseless theory of time:

 

I.     Arguments for a Tensed Theory of Time

       A. Tensed sentences, which can neither be translated into synonymous tenseless sentences nor be given tenseless, token-reflexive truth conditions, correspond, if true, to tensed facts.

       B. The experience of temporal becoming, like our experience of the external world, is properly regarded as veridical.

 

II. Refutation of Arguments against a Tensed Theory of Time

       A. McTaggart’s celebrated paradox is based upon the misguided marriage of a tenseless ontology of events or things with objective temporal becoming, as well as the unjustified assumption that there should exist a unique, complete description of reality.

       B. The passage of time is not a myth, but a metaphor for objective temporal becoming, a notion which can be consistently explicated on a presentist metaphysic.

 

  III. Refutation of Arguments for a Tenseless Theory of Time

       A. Temporal becoming is compatible with Relativity Theory if we reject space-time realism in favor of a neo-Lorentzian interpretation of the formalism of the theory.

       B. Time as it plays a role in physics is a pale abstraction of a richer metaphysical reality, omitting indexical elements such as the "here" and the "now" in the interest of universalizing the formulations of natural laws.

 

 IV. Arguments against a Tenseless Theory of Time

       A. In the absence of objective distinctions between past, present, and future, the relations ordering events on a tenseless theory are only gratuitously regarded as genuinely temporal relations of earlier/later than.

       B. The claim that temporal becoming is mind-dependent is self-defeating, since the subjective illusion of becoming involves itself an objective becoming in the contents of consciousness.

       C. A tenseless theory entails perdurantism, the doctrine that objects have spatio-temporal parts, a view which is metaphysically counter-intuitive, incompatible with moral accountability, and entails the bizarre counterpart doctrine of transworld identity.

       D. A tenseless theory is theologically objectionable, since its claim that God and the universe co-exist tenselessly is incompatible with a robust doctrine of creatio ex nihilo.

 

Please consult the books if you’re interested in the enjoyable details!

As intimated in (III.A) above, I consider spacetime to be a diagrammatic way of representing our world of space and time in a 4-dimensional geometrical fashion, in which three dimensions represent space and one represents time. Such a representation has tremendous instrumental value due to its simplicity and clarity, but it should not be invested with reality. So spacetime is not really curved, since spacetime does not really exist. Rather gravitation, which is actually one of the four fundamental forces of nature, can be represented as spacetime curvature. Some physicists like Steven Weinberg have even complained that the geometrical representation of gravitation as spacetime curvature has actually hampered the quest for a unified physics that would reduce all four forces of nature to a single fundamental force. In any case, spacetime is not expanding; rather it is space which is expanding over time. But on spacetime realism, spacetime is immobile, since it is not embedded in a higher dimensional hyper-time. It just exists tenselessly, and time is merely an internal parameter of the geometry.

Your question has theological significance because if time is tensed and temporal becoming is real, then it seems that God must exist in time, not timelessly, at least since the moment of creation, in light of God’s changing knowledge of tensed facts and His causal connection to a world of changing things.

- William Lane Craig