Original article

MIT News: https://news.mit.edu/2026/using-reason-again-and-again-brian-hedden-0802

Introduction

Philosopher Brian Hedden argues for “time-slice rationality”: rationality may be better evaluated at particular moments rather than as a property of a person extended across an entire lifetime. Useful for IELTS philosophy and social-science reading.

Vocabulary

rationality — reasoning sensibly from evidence; skeptical — doubtful; circumstance — condition surrounding an event; temporally extended — existing across time; locus — central location of something; streamlined — made simpler and more efficient; epistemology — philosophy of knowledge; anticipate — expect in advance; sunk cost — an unrecoverable past cost; deliberate — think carefully; counterproductive — producing the opposite of the intended effect; hindsight bias — seeing past outcomes as more predictable after they occur; reassessment — evaluating again; contrarian — opposing a prevailing view.

Reading comprehension

1. What does “time-slice rationality” mean?

Reference answer
Rationality should primarily be judged from the evidence and reasons available to a person at a particular moment.

2. Why are past and future selves compared to teammates?

Reference answer
Different temporal versions of a person can have different information and interests, so cooperation across time resembles coordination among different people.

3. How does the gym-membership example illustrate the theory?

Reference answer
A decision that once made sense can later cease to be rational when circumstances change; past expenditure alone should not determine the present choice.

4. Why might some apparent hindsight bias actually be rational reassessment?

Reference answer
New evidence available after an event can rationally change one’s assessment, so not every retrospective change of belief is a cognitive error.