The RaM"a (Y"D 87:6) cites an opinion that one may shouldn't stoke a flame beneath a non-Jew's pot, for fear that there's some milk and meat residue in it, and you might come to cook said milk and ...
In this answer, I proposed that since there is a machlokes rishonim on a certain issue, it counts as a safek (doubt), although the Shulchan Aruch rules strictly. DoubleAA commented, saying that he ...
Halacha depends on the facts of a situation. Generally, when one cannot know the exact facts, he is expected to assume that they are as usual (rov), or as they were when last checked (chazaka). When ...
If someone is unsure if he recited Tal UMatar, one has to repeat the Shemoneh 'Esreh (it's slightly more complicated, but let's keep it simple). If one is unsure if he remembered to Bentch (recite ...