Melacha on Shabbat - At which stage of removal does something become legal?

Question

I had heard of something relating to melacha on Shabbat from an (orthodox!) rabbi who mentioned something really interesting. At a certain level of removal, one can indirectly perform melacha. It was something to the effect of a rube goldberg action wherein one starts one reaction which isn't melacha which in turn starts another reaction which isn't melacha which starts another reaction which isn't melacha which, finally, starts a reaction that is melacha, and somehow this is kosher.

I suppose the premise is that at a certain level, it's not guaranteed that you're doing something and something in the multiple reactions could fail, so it removes you a certain distance which makes it extremely unlikely for you to break Shabbat or Yom Tov. I've also heard of this applying to kosher ovens which can be turned on during Shabbat or Yom Tov as well as wheelchairs and certain motion-sensing cameras. What is the actual halacha of this and does it really apply as above (by a certain level of removal from the prohibited act)?

Answer 1

It's known as grama, or "indirect causation."

It was written up well in a Journal of Halacha & Contemporary Society article many years ago, I believe as:

Rabbi Tzvi Sendler, Gramma in Halacha, XXXIX, 23

(And Jake, it's not as clear that the same concept would apply to other mitzvahs; the threshold for Sabbath-prohibited labor is higher because it must be melechet machshevet, "concentrated labor.")

One way to accomplish grama involves a five-second delay between your action and the result (well maybe a bit less than five seconds, long enough to say "Greetings and blessings, my dear teacher and master!"). This is employed by Rabbi Moshe Heinemann in Sabbath-mode ovens, which may have their temperature adjusted on holidays (but not Shabbat).

Many other grama devices are available in Israel; I'd heard of a patrol car that had grama mode for normal patrol, but then could be switched to ordinary mode if there was an emergency.

There's even talk of things like a grama light switch (the switch doesn't turn the light on, it just removes something that had been keeping the light off), though regardless of the internal mechanism, you could argue that a push-button reaction is no longer "indirect." I heard from Rabbi Herschel Welcher that Israeli halachic authorities are more inclined towards allowing grama switches; American rabbis aren't, but in America it's easy to find a non-Jew handy who can turn on/off the light.