Disclaimer: This book was written as part of a research internship at the Center for Reducing Suffering. All opinions are my own.
The Case Against The Stars can be accessed here: The Case Against The Stars | Zenodo
Executive Summary
Longtermists frequently contend that space colonisation has high expected value.[1] After all, a vast number of future beings might come to exist if other star systems are settled.
However, the desirability of space colonisation has not yet received sufficient evaluation, especially from suffering-focused perspectives.
The Case Against The Stars provides the first systematic critique of the longtermist case for space colonisation. By surveying risks of astronomical suffering ("s-risks") associated with activities in space, the book argues that we ought to refrain from initiating colonisation processes unless and until robust suffering-mitigating constraints are demonstrated.
Contributions of the Book
The book provides several original contributions to literature on longtermism, suffering-focused ethics, and space ethics:
It is structured as follows:
The introduction explains “suffering-focused ethics” - why the prevention and alleviation of suffering constitutes an important aspect of ethical living.
Chapter 1 examines the most sophisticated case for the claim that space colonisation is desirable, explaining its assumptions and core claims which shall be assessed throughout the rest of the book.
Chapters 2-5 argue that colonising space risks bringing about the astronomical suffering of sentient beings. Analytic codas at the end of each chapter provide illustrative quantitative estimations of the scale of suffering associated with such risks.
Chapter 2 discusses risks faced by biological organisms, covering the expansion of factory farming at scale, the seeding of evolutionary processes on distant planets, and the construction of biospheres through terraforming projects.
Chapter 3 assesses risks to human colonists, including the entrenchment of totalitarian regimes and the initiation of warfare.
Chapter 4 considers risks pertaining to artificially sentient beings, covering digital minds, simulated beings, and expansionist civilisations competing at the frontier.
Chapter 5 synthesises the risk landscape, arguing that these risks are difficult to prevent, relatively technologically feasible, plausibly astronomical in magnitude, and carry a non-negligible probability of occurring once colonisation processes have been initiated.
Chapter 6 examines the significance of the potential existence of extraterrestrial civilisations to the desirability of space colonisation. It critiques the view that humanity might robustly alleviate and prevent the suffering of extraterrestrial organisms by colonising space.
Chapter 7 directs the focus back onto the case for space colonisation, arguing that even if we accept nearly all of the proponents’ assumptions, we ought to refrain from colonising space unless and until humanity is able to reliably preclude associated risks. It presents and defends a precautionary argument, two auxiliary arguments, and responses to three objections.
As a preview of the precautionary argument, consider the following:
P1: For any action A, if
Then one ought not perform A now.
P2: The initiation of irreversible processes of space colonisation - such as directed panspermia, establishing self-sufficient, autonomous colonies, and the creation of vast biological and digital populations - satisfies (a)-(d).
Therefore,
C: One ought not initiate irreversible processes of space colonisation now.
If this line of reasoning strikes you as interesting and as warranting further discussion, you may appreciate a close reading of the book's claims.
I believe that it would be most helpful for readers who are either i) longtermists who advocate expansion into space, ii) space governance researchers who wish to consider risks of astronomical suffering and their prevention, or iii) suffering-focused ethicists who would appreciate ways to analyse and compare s-risks and magnitudes of suffering across scenarios.
For a bibliography, see The Case Against The Stars | Zenodo.
The importance of space colonisation to longtermist assessments of the future can be seen in Bostrom, 2003a, Armstrong and Sandberg, 2013, and Greaves and MacAskill, 2025.
From this summary I don't know what the book's arguments are, nor what original pro-colonization arguments it is responding to. (x-risk?)
Interesting topic though, and sounds like a good book from what I can tell. Thanks for the alert and invitation to read it.
Is there a "right size" for space colonization, (one solar system, a few nearby stars, one galaxy)? Or is it basically inevitable that any space colonization is going to lead to infinite expansion?
Thanks for this Tandena. Apologies if the summary is unclear. The book argues that we ought to refrain from initiating effectively irreversible space colonisation processes unless and until robust suffering-mitigating constraints are demonstrated.
By "effectively irreversible processes," I am referring to actions such as sending probes containing microbes to seed life on distant star systems (directed panspermia), establishing independent colonies capable of further expansion, sending out Von Neumann probes, and so forth. These leaves upon colonisation at intra-Solar System scales, which I argue may be more reliably governed.