I have seen Rationalism mistaken for sound proof used in lot of arguments.Comfortably, ignoring that the validity of the conclusion is dependant on the validity

I have seen Rationalism mistaken for sound proof used in lot of arguments.Comfortably, ignoring that the validity of the conclusion is dependant on the validity of the premises. To be honest, logical reasoning is very useful in designing experiments, and multiple chains of logical reasoning is not my strongest point, but the refusal to define the conclusions beforehand is what makes me suspicious, when someone uses long chains of reasoning to convince me.