Mathieu Rees, a software engineer with a philosophy PhD from the University of Leeds, is the winner of the 2025 Sanders Prize in Metaethics.

Rees was awarded the prize for his paper, “Abductive Arguments for Ethical Error-Theory: The Relevance of Non-Cognitivism.”

Here’s the abstract of the paper:

Given its avoidance of explanatory appeals to ethical reality, non-cognitivism is seemingly open to an abductive argument for ethical antirealism, and hence error-theory. Many non-cognitivists would want to avoid this result. I argue that doing so is far from straightforward. In the first instance, non-cognitivists have no distinctive resources for resisting abductive arguments for antirealism. Moreover, while some non-cognitivisms can block the step from antirealism to error-theory, one can reasonably question the theoretical virtue of non-cognitivism itself. The abductive case for non-cognitivism sans error-theory is in uncertain shape.

You can read the whole paper here.

The prize is awarded by the Marc Sanders Foundation and administered by Russ Shafer-Landau, Professor of Philosophy at the University of Wisconsin, Madison.

The prize is $5,000 and publication of the winning essay in Oxford Studies in Metaethics.

You can learn more about the prize and see a list of previous winners here.