Open Discussion: What role do thought experiments play in philosophy?

This meeting will be a live discussion of the title topic. This sort of discussion can't be settled in any particular way, but remains relevant for beginners and initiates to philosophy.

(Note: after meetings, attendees are all welcome to join for dinner. We typically go to one of a few local restaurants in walking distance of the meetup location.)

Here are some questions and comments that may help guide the conversation (feel free to bring questions of your own, as well):

Despite the abstract nature of much philosophy, thought experiments have always played a role in framing its considerations. But what role do they actually play?

Can philosophy really accomplish its ends without such thought experiments? If Descartes didn't write about the evil demon, would he have still needed something like this thought experiment (even under different terms) to frame his thinking?

What is an experiment in thought? Normally, we think of an experiment as taking place outside of us, but with our anticipations guiding us in drawing certain information from it. What is it to have an experiment where we are (apparently) providing everything?

If we frame our experiments differently, do we produce different philosophies? Do our thought experiments usually play a negative role: counterfactuals serving to contradict general or universal assertions?