The Bavli, Shabas 37 amud 1, wonders about the permissibility of placing a pot of food adjacent to a stove-oven (rather than atop or in it) when the stove-oven has good fuel in it that has not been cooled. Its second attempted proof succeeds in proving that one may not do so. It then asks "What is the result?" and proceeds to bring another proof (that one may do so). Why doesn't it accept the valid proof of impermissibility?
The proof is as follows: Rav Chiya says a cooled oven that then caught fire again can have a pot of food placed near it. The implication is that an oven that has not been cooled (which is our question) cannot have a pot of food placed near it. (Attempts to discredit that implication by arguing that the case was mentioned by the way and not specifically — and so cannot be inferred from — are refuted.)