Cambridge change


A Cambridge change occurs when a predicate P is true of object O at this moment but is not true of O the next moment, not because O's bodily constitution is no longer the same, but because some difference in the constitution of an object G makes logically necessary the passage of the original predicate from true to not true.

History

The term Cambridge change was coined by Peter Geach in the late 1960s because the influential Cambridge University philosophers Bertrand Russell and J. M. E. McTaggart used examples of such changes in their work.

Example

Last year Mary, who stands five-foot-four, was taller than her five-foot tall, 13-year-old son John; today Mary is shorter than her now five-foot-six, 14-year-old son. Mary has undergone a Cambridge change.
The Cambridge change that Mary has undergone consists in the fact that a predicate true of her last year is not true now, and a predicate not true of her last year is now true; but the change in the predicates’ truth values is not grounded in any change in her height. By contrast, the change in the truth value of last year's and this year's statement about John's height reflects his growth.
Some philosophers have proposed that a Cambridge change is a change in an individual's extrinsic or relational properties; genuine changes involve intrinsic ones.