Unthink

They at least had the immense and mighty imagination of which I speak; they could unthink the past. They could uncreate the Fall. With a reverence which moderns might think impudence, they could uncreate the Creation.

But to do so consistently would require a fairly radical revision of the concept. We should have to unthink as far back as Aristotle […]

In An Experiment with an Air-Pump, characters repeatedly assert that "once you've thought something, you can't unthink it, can you?"

"You must learn to edit your thoughts," she said. "Unthink them..."