Do you mean generally speaking or within a particular context?
Sure, but unfortunately, many aren't anywhere near as rational as they've convinced themselves they are.
Discussion
Humans don't always behave rationally, but they do always behave reasonably. In that I mean, there is always some reason for their behavior, even if they are not self-aware enough to recognize it.
They are often working off of assumptions or axioms, or responding to changes in their environment.