The Philosophy of the Search for Extraterrestrial Life

Many scientists are optimistic that we will soon discover evidence of life beyond Earth. In my new book, Will We find Life Beyond Earth? The Philosophy of the Search for Extraterrestrial Life, I take a philosophical approach to this optimism. I argue we won’t find life any time soon. If you would like to see the manuscript, let me know.

In the meantime, try this popular piece at the Institute of Art and Ideas, this podcast, or the papers below.

The Search for Biosignatures

These papers are about the search for biological life on Mars and planets beyond our own solar system.

  • Will We Discover Life Beyond Earth?
    Paper under review
    We have yet to find any actual evidence of life beyond Earth. So why do so many people seem to think we will? I present, categorise, and assess the major arguments. The result is, I claim, surprisingly underwhelming.
  • A Modal Epistemology of the Search for Extraterrestrial Life.
    Paper under review
    What evidential standard or threshold would we have to meet in order to succeed in the search for life beyond Earth? I argue that existing astrobiological practice is committed to a modal rendering of the standard, approximating the familiar epistemic principle, Safety.
  • What is a Biosignature and Why Does it Matter? A Philosophical Analysis.
    Forthcoming at Philosophical Problems in Science: Astrobiology Special Issue.
    Astrobiologists often use the concept of a biosignature. I show why existing philosophical analyses of the nature of this concept fail and propose an alternative. Before arguing that none of this matters!
  • Comparing Astrobiologists’ Confidence in Extraterrestrial Life Claims for K2-18 b and Cheyava Falls.
    Nature Astronomy (Co-authored).
    A quantitive survey of the scientific community regarding recent potential biosignatures on Mars and a distant exoplanet, led by my colleague Peter Vickers.
  • Optimism in the Search for Extraterrestrial Life: A Philosophical Perspective.
    Proceedings of the Aristotelian Society (2025).
    Why are so many scientists confident that life exists in large quantities beyond Earth? This paper is an early attempt to formulate a problem with the obvious answers.
  • New Work on Biosignatures.
    Mind (2023).
    The concept of a biosignature is often appealed to. I explain why existing accounts fail and propose an alternative.
  • Confidence of Life Detection: The Problem of Unconceived Alternatives.
    Astrobiology (co-authored, 2023)
    A co-authored that proposes a scale for measuring confidence in having found life.

The Search for Technosignatures

These papers are about the more speculative search for signs of intelligent life.

  • Methodological Conservatism in the Assessment of Unidentified Anomalous Phenomena.
    Forthcoming at Ergo
    A paper about the epistemic assumptions in a recent NASA report about UFO.