There are times when Chazal says something and the meaning is debated and there are other times when whether an entire category even exists. How is this so? To give specific examples of what I'm referring to. In Yore Dea Basar B'chalav there is a a debate about fish that came in contact with meat kelim and whether there is enough taste to then forbid eating with fish. The phrase the gemera uses is "alav" "to place". It discussed in shulchan aruch whether this can include cooking and if so what types are included with the phrase the gemera uses.
A different type of disagreement is where they disagree whether something exists at all. For example: The Rema holds there is rabbinical "chanon" (chatika nases nevela. something which becomes like a nevela) that can come for prohibitions aside from "basar b'chalav" (milk and meat) while the Mechaber holds there is no such Rabbinical catigory of "chanon" and there is only the Torah category of "chanon" which is the result of "basar b'chalav".
Either Chazal made the Rabbinical prohibition or they did not. How then could there be a disagreement like this?
