Non-Identity Problem, explained.
The non-identity problem concerns evaluating actions that influence both future welfare and the identities of the people who will exist.
Why it happens
A fast policy gives A a positive welfare index forty; a delayed policy gives eighty either to A or to a different person B. Switching identities changes the availability of a simple person-level counterfactual comparison.
The non-identity problem concerns evaluating actions that influence both future welfare and the identities of the people who will exist.
Read the result
Compare the identity labels before making a worse-off claim. Positive welfare in one row does not by itself establish that a policy is permissible.
A worked example
Change who exists under the alternative policy
Inspect the same-person mode, where A has welfare forty or eighty under the two policies.
Switch to different people so the cleaner policy brings B rather than A into existence.
Identify why A’s counterfactual life at eighty is no longer supplied, while ethical questions about the policies remain.
OPTIONAL DEEPER DETAILGo deeper: inside the model
Inside this model
A fast policy gives A a positive welfare index forty; a delayed policy gives eighty either to A or to a different person B. Switching identities changes the availability of a simple person-level counterfactual comparison.
Where this idea is useful
A practical use
Separate improving an existing person’s possible future from comparing policies that create different future people.
A common misconception
“If a different person would exist, every identity-affecting policy is justified.”
A missing simple person-level harm comparison does not settle rights, distribution or broader obligations to future people.
What this explanation leaves out
- Welfare indices are invented and positive. Rights, effects on existing people and distribution are omitted; lack of a worse-off identical person does not establish permissibility.
Are forty and eighty empirical measures of possible lives?
No. They are positive invented indices used to expose an identity-dependent comparison, not measurements or policy forecasts.
Does the counterfactual change someone’s life or change which person has a life?
Associated thinkers
Associations marked provisional are awaiting source review.
Further reading
Explore the original research or the teaching reference behind this experiment.