Currently I'm using the phrase "Operating on the premise that". Here's an example:
Operating on the premise that the God depicted in the Old Testament is real, I would provide a sacrificial lamb.
I want to be able to talk about this practice in the abstract.
When I am [new abstraction]ing, I'm able to empathize better and learn from my new frame of mind.
I could establish an acronym (OOPT) and refer to the practice as OOPTing but I feel like logicians or writers must have already solved this, as it's a fundamental behaviour in a lot of practices.