Does Changing Your Mind Show the Earlier Decision Was Irrational?

On Monday the forecast is clear, so you plan an outdoor gathering for the weekend. On Friday a severe-rain warning arrives, and you move it indoors. The second decision differs from the first, but that does not show that the first was irrational. Rationality usually does not require an unchanging conclusion; it requires action to respond to the reasons available at the time.

Contemporary theories of reasons for action distinguish the reasons there are to act from the reasons for which a person actually acts. Normative decision theory asks how choices should be made under uncertainty by considering probabilities and outcomes. Both points warn against judging a decision only by what became known later. If reliable evidence on Monday supported the outdoor plan, that choice could have been reasonable even though the weather later deteriorated. New evidence on Friday changed the structure of the reasons, so revising the plan could also be reasonable.

Yet the fact that people change does not excuse every reversal. If the facts, commitments and stakes remain the same, abandoning a plan merely because of a passing mood still deserves scrutiny. My view is that what should remain stable is not the conclusion but the coherence of the reasons: do not retreat from a commitment merely for convenience, and do not mistake stubbornness for principle when revision is warranted.

https://plato.stanford.edu/entries/reasons-just-vs-expl/
https://plato.stanford.edu/entries/rationality-normative-utility/