BJPS Popper Prize 2021

We are delighted to announce that the winner of the BJPS Popper Prize for 2021 is Eddy Keming Chen.

The citation from the Editors-in-Chief can be found below. The BJPS Popper Prize is awarded to the article judged to be the best published in that year’s volume of the Journal, as determined by the Editors-in-Chief and the BSPS Committee. The prize includes a £500 award to the winner(s). More information about the prize and previous winners can be found here.

The following two articles were also singled out for honourable mention:

  • Lauren N. Ross

    ‘Causal Concepts in Biology: How Pathways Differ from Mechanisms and Why It Matters’, 72, pp. 131–58


In ‘Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State’, Eddy Keming Chen offers a unified solution to two difficult problems in the foundations of physics: what gives rise to the arrow of time and how to characterize quantum ontology. While it is often assumed that the real quantum state of the universe must be pure, Chen argues that density matrix realism, which permits mixed quantum states represented by density matrices, has significant and unexpected advantages, if we also adopt a new version of the past hypothesis. In particular, he proposes the initial projection hypothesis, according to which the density matrix representing the initial quantum state of the universe is not just compatible with a low-entropy boundary condition, but uniquely specified: it is the normalized projection onto the past-hypothesis subspace. From the perspective of Chen’s framework, the initial quantum state becomes a good candidate for a simple law; there is no need for a probability distribution over initial quantum states; and the foundations of quantum mechanics and foundations of statistical mechanics are found to be intimately connected.

As an ambitious, novel contribution to major issues in the foundations of physics, the BJPS Co-Editors-in-Chief and the BSPS Committee consider Chen’s paper to be a very worthy recipient of the 2021 Popper Prize.

—Prof. Wendy Parker & Prof. Robert Rupert