Philosopheasy Editorial Ledger
Curated and annotated by the Philosopheasy Editorial Board as part of the series on Ideas Surviving Outside the Algorithmic Consensus. [Estimated reading time: 5 mins]
Consider a simple addition. If we have a prosperous society, and we add a separate, isolated group of people whose lives are barely worth living, have we made the world worse? They do not harm the original group, and their own lives are positive. Yet, this innocent step is the first slide down a logical precipice. The Mere Addition Paradox is the engine that drives population ethics into its most uncomfortable corner.
The Three Steps of the Paradox
The paradox is structured around three distinct population states, designed to show that our intuitive moral judgments are intransitive—meaning they lead to logical contradictions when chained together:
- Population A: A small population with an extremely high quality of life.
- Population A+: The same high-quality population A, plus an entirely separate group of people with a lower, but still positive, quality of life. Intuition suggests A+ is not worse than A, as no one has been harmed and new positive lives have been created.
- Population B: A population equal in size to A+, but with resources redistributed so that everyone has an equal quality of life that is slightly lower than A's average, but significantly higher than the added group's average in A+. Intuition suggests B is better than A+ due to the moral value of equality.
The paradox exposes a deep flaw in our incremental moral reasoning. In modern policy and corporate governance, we make "incremental improvements" that seem harmless or mildly positive in isolation, yet cumulatively degrade the systemic quality of our cultural and social environments. We optimize the parts while destroying the whole.
If B is better than A+, and A+ is not worse than A, then B must be better than A. By repeating this logic, we are forced to conclude that a world of trillions of people living lives barely worth living (Population Z) is superior to the original, blissful Population A. This is the core of Parfit's challenge to rational ethics.
Textual Citations & Original Sources
- Derek Parfit, Reasons and Persons, Chapter 19: "The Mere Addition Paradox" (1984). The original formulation of the three-step population comparison.
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