This is a special case of BP841 and a generalisation of BP822.

The process that turns one object into the other is the same both ways vs. the process changes depending on which object is chosen as the starting point.

The process that turns one object into the other is the same both ways vs. the process changes depending on which object we choose as the starting point.

The process that turns one object into the other is the same regardless of which object we choose as the starting point vs. The process that turns one object into the other changes depending on which object we choose as the starting point.

https://en.wikipedia.org/wiki/Duality_(mathematics)

https://en.wikipedia.org/wiki/Involution_(mathematics)

This is, in a sense, a special case of BP841 and a generalisation of BP822.

Leo Crabbe