Read part 1: Joseph Diekemper argues that the present is only a border between past and future.
Read part 2: Julian Barbour replies that arguing over past and future is to miss what really matters.
Read part 3: Diekemper underlines the necessity of philosophy to our understanding of time.
Read part 4: Barbour disagrees: science will ultimately always take precedence over philosophy.

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In response to Joseph Diekemper, I think science will ultimately always take precedence over philosophy, which, I would say, is at its best when questioning existing concepts and suggesting ideas to science.

Moving on to the specific points, Diekemper says his "definition of the passage of time would be stated in terms of events having occurred". But how do you know an event has occurred? I think the minimum requirement is a difference in the world; I should have emphasized difference rather than change. Moreover, in connection with what we call the passage of time, the nature of the difference is generally very characteristic. Take two photos of me a decade apart. They are different; moreover, the whole Julian looks older in one than in the other. It is not the case that my face looks older but my hands younger.

When it comes to real disagreement, Joseph says my view "entails that the change which we both take to be fundamental to our experience of time is illusory and non-existent. There is no real change on his view, there are just three-dimensional slices – the Nows – eternally coexisting, and these never change."

I agree that in my view each Now is fixed once and for all. But, first, every Now is richly structured and, second, every Now is different from every other Now. And, if my concept is correct, all the Nows can be arranged uniquely in a timeline on the basis of the differences between them. Neither the structure in each Now nor the differences between them is illusory.

What we call the passage of time has three aspects: first, what we experience in each instant is richly structured (certainly if we have our eyes open); second, no two instants are exactly alike; third, we see things moving. Of these three I only question the third (I suspect it is an artefact of the brain's creation of what we experience in consciousness). The first two are definitely not illusory. Thus, when Joseph claims my theory implies "every aspect of our experience of the world would be pervaded by illusion", that is definitely not correct. I have never dreamed of denying the first two of the aspects of experience I listed above. I don't think anyone would do that. I only question the fleeting third. In that, I am certainly not alone.

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Read part 1: Joseph Diekemper argues that the present is only a border between past and future.
Read part 2: Julian Barbour replies that arguing over past and future is to miss what really matters.
Read part 3: Diekemper underlines the necessity of philosophy to our understanding of time.
Read part 4: Barbour disagrees: science will ultimately always take precedence over philosophy.