Changing the past and the future

This passage from Terry Pratchett’s Equal Rites has me thinking about hind- and foresight.

“Granny had nothing against fortune-telling provided it was done badly by people with no talent for it. It was a different matter if people who ought to know better did it, though. She considered that the future was a frail enough thing at best, and if people looked at it hard they changed it.”

The idea that observing X changes X is common enough, but we never really apply it in the realm of our own personal past and possible futures. For example, if I extrapolate and consider a future in which I eat pizza, watch Netflix and exert absolute minimum effort in my work the chances are I’ll change my future, possibly for the better. And if I deliberately examine select parts of my past they take on a new importance, a greater salience, and thus are changed to me.

Observation changes the observed; hindsight and foresight are not passive but active uses of perception.