Can the past hypothesis explain the psychological arrow of time?

Meir Hemmo, Orly Shenker

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

1 Scopus citations


Can the second law of thermodynamics explain our mental experience of the direction of time? By this experience, we mean our psychological feel of distinction between the past and the future; we call this experience the ‘psychological arrow of time’. An influential approach (for example, by Albert and Loewer) argues that the second law gives rise to the psychological temporal arrow. On this approach, accounting for the temporal directionality of the second law in terms of fundamental physics (which is time-symmetric) requires introducing the past hypothesis of low entropy. The idea is that the directionality of the universal increase of entropy explains how the psychological arrow comes about. We argue that there are two necessary conditions on the workings of the brain that any account of the psychological arrow of time must satisfy, and we show that the past hypothesis of a universal low entropy state does not satisfy these conditions. We propose a new reductive (physical) account of the psychological arrow compatible with time-symmetric physics, according to which our two necessary conditions are sufficient. Our proposal has some radical implications, for example, that the psychological arrow is fundamental, whereas the temporal direction of entropy increase in the past hypothesis is derived from it, rather than the other way around.

Original languageAmerican English
Title of host publicationStatistical Mechanics And Scientific Explanation
Subtitle of host publicationDeterminism, Indeterminism And Laws Of Nature
PublisherWorld Scientific Publishing Co.
Number of pages33
ISBN (Electronic)9789811211720
StatePublished - 1 Jan 2020

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© 2020 by World Scientific Publishing Co. Pte. Ltd.


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