A is not always A
Let's dispel the common notion that 'A' is 'A', which is only true in certain rigidly defined systems, like math or logic. The statement is not without validity; plus it has great utilitarian value. As an assumption or axiom, it is the very basis for logical deduction and for most mathematical truths; however, it is unwise to use the statement as a basic philosophical premise.
At least as long ago as Heraclitus, the ancients knew that things changed. An acorn becomes an oak; the new day is not yesterday. In the short time that it will have taken to read this paragraph, the universe will have expanded in size by hundreds of thousands of miles, your life has quickened toward its end, and ‘A’ has become something other than ‘A’.
The uncritical acceptance of any axiom, assumption or maxim can lead to weary years of stagnant thought. Something of this nature occurred with the belief that Euclid’s postulates were true. For two thousand years no one challenged him. And when someone did, finally, things changed.
Other kinds of things change too. In fact, this is a very strange thing about the universe at large. In general, things fall apart. (Or, more correctly, things become more and more disorganized.) Sometimes this seems hard to see or to understand. One reason is that humans are constantly spending energy to inject intelligible organization and direction into the world around them. But if one builds a house, for instance, and just lets it sit there. Those disorganizing forces become quite evident. Paint peels and the gutters break. The wild moves in.
That is the nature of things.