A Common Misunderstanding of So-Called Cambridge Changes
There are philosophers who think that so-called ‘Cambridge’ changes and real changes are mutually exclusive. Thus they think that if a change is Cambridge, then it is not real. This is a mistake. Real changes are a proper subset of Cambridge changes.
Consider an example. Hillary gets wind of some tomcat behavior on the part of Bill and goes from a state of equanimity to that lamp-throwing fury the Bard spoke about. ("Hell hath no fury like a woman scorned!"). Bill, on the other hand, as the object of Hillary’s fury, also changes: at one time he has the property of being well thought of by Hillary, and the contradictory property at a later time.
Common to both the real change (in Hillary) and the relational change (in Bill) is the following: X changes iff there are distinct times, t1 and t2, and a property P such that X exemplifies P at t1 and ~P at t2, or vice versa. Change thus defined is Cambridge change. The terminology is from Peter Geach:
The great Cambridge philosophical works published in the early years of this [the 20th] century, like Russell’s The Principles of Mathematics and McTaggart’s Nature of Existence, explained change as simply a matter of contradictory attributes’ holding good of individuals at different times. Clearly any change logically implies a ‘Cambridge’ change, but the converse is surely not true. . . . (Logic Matters, University of California Press, 1980, p. 321.)In sum, every (alterational) change is a Cambridge change, but only some of the latter are real changes. The rest are mere Cambridge changes. It is therefore a mistake to think that Cambridge and real changes form mutually exclusives classes. What one could correctly say, however, is that mere Cambridge changes and real changes form mutually exclusive classes.
But what about existential (as opposed to alterational) change, as when a thing comes into existence, or passes out of existence? Are such changes real changes in the things that pass in and out of existence? Are they merely Cambridge changes? Or neither? Treatment of this hairy topic is best postponed.