Robert asked:

What is the age of the Earth if time does not exist?

Answer by Geoffrey Klempner

This is a nice question, which illustrates the difference between a metaphysical proposition and an empirical or mundane claim.

If it is a metaphysical truth that time does not exist, or is ‘unreal’ as McTaggart argued in The Nature of Existence (1921-7), then there is no past or future, nothing is young or old, time does not pass. Does that mean that everything remains the same? No, because ‘remaining the same’ itself implies temporal distinctions. The houses outside my window remain the same while the clouds move.

A similar point could be made about the size of the Earth if matter and the physical universe do not exist, as Berkeley claimed in his philosophy of immaterialism. From a metaphysical standpoint, there are no ‘material’ objects. All reality exists as ideas in the mind of God. Yet the world of our experience exhibits differences of physical size and mass ‘as if’ there were material things.

Even for a McTaggart, there are mundane or empirical truths which are unaffected by one’s metaphysical theory. ‘It’s now time for tea,’ as the tea lady knocks on the door of the philosopher’s study and McTaggart takes a break from writing his great metaphysical treatise. In these terms, the Earth has an age whether metaphysically time is real or not.

In the heyday of Oxford philosophy, this double stance was regarded with great suspicion. J.L. Austin put the point succinctly in the context of theories of perception: ‘There’s the bit where you say it and the bit where you take it back’ (Sense and Sensibilia, 1962).

Would Austin similarly complain that my desk top is solid wood but also from the point of view of fundamental physics mostly empty space? It seems a perfectly reasonable thing to say. Depending on one’s interests — which include theoretical interests from physics, or metaphysics, or some other way of describing the world — the properties we attribute to things vary. The very meanings of the words we use vary. I don’t have a problem with that.