write-once

You can't make the truth not be. Once it is written, it cannot be unwritten. You can add to the truth and thus change it, but you cannot remove what is, once it is. If you make a mistake, you can never not have made it. But you can fix it, if it's the sort of mistake that can be fixed, and thus bring the sum of some facet of the truth back to where it was. And, probably, that facet is what you wished to change to begin with.

The universe is write-once memory.