Part 2 focuses on the relationship between rationality and time, dealing with questions such as: should we take into account our past desires?, should I do something I will regret later, even if it seems a good idea now?, and so on.

For example, Parfit asks the reader to imagine entering a "teletransporter," a machine that puts you to sleep, then destroys you, breaking you down into atoms, copying the information and relaying it to Mars at the speed of light.

Parfit resolves the logic to reach this conclusion, which appears to justify incursion into personal freedoms, but he does not explicitly endorse such invasive control.

Parfit's conclusion is similar to David Hume's bundle theory, and also to the view of the self in Buddhism's Skandha, though it does not restrict itself to a mere reformulation of them.

Bernard Williams described Reasons and Persons as "brilliantly clever and imaginative", and commended it as part of a wave of work in analytic philosophy that deals with concrete moral problems rather than abstract meta-ethics.

[1] Philip Kitcher wrote in his review of Parfit's On What Matters that Reasons and Persons "was widely viewed as an outstanding contribution to a cluster of questions in metaphysics and ethics".

[2] Peter Singer included Reasons and Persons on a top ten list of favourite books in The Guardian, stating that "Parfit's penetrating thought and spare prose make this one of the most exciting, if challenging, works by a contemporary philosopher".

Strawson gave the book a positive review, stating "Very few works in the subject can compare with Parfit’s in scope, fertility, imaginative resource, and cogency of reasoning".

[4] In an interview, David Chalmers said that he "loved" Reasons and Persons, saying that it gave him a "sense of how powerful analytic philosophy can be when done clearly and accessibly.