  Change is so pervasive in our lives that it almost defeats description and analysis. One can think of it in a very general way as alteration. But alteration in a thing raises subtle problems. One of the most perplexing is the problem of the consistency of change: how can one thing have incompatible properties and yet remain the same thing? Some have held that change is a consistent process, and rendered so by the existence of time. Others have held that the only way to make sense of change is as an inconsistency. This entry surveys the history of this problem and cognate issues, and concludes that the case for change as inconsistency cannot be dismissed so easily.