Lighting A Fire Under A Pot
The Rema (Yoreh De’ah 87:6) has a different approach. The principle of davar she’eino miskaven applies to other matters as well. Let us take, for example, the case of cooking meat with milk. Not only is it forbidden to eat meat and milk together, the cooking itself is biblically forbidden even if one does not intend to eat the food. Therefore, the Rema rules that one may not light a fire under a pot belonging to a gentile without first ascertaining what’s inside: the pot might contain meat and milk, and by cooking them together one would transgress the said prohibition. Similar to the case of the box with flies, the element of uncertainty here does not involve the action, since lighting a fire will definitely cook the food in the pot. The element of uncertainty is the situation in the background of the action. Does the pot contain meat and milk?
The Rema rules that this is not a case of davar she’eino miskaven. It is a case of retroactive pesik reisheih – and it is forbidden.