I guess both Mulder and Scully are strong T's. The whole series has this strong T-ish atmosphere.
They show no sign's of the NF's "please, love me"-attitude but keep their cool and stay detatched and both are obsessed with truth ("the truth is out there" ). What are your arguments to see him as an F?
It's definitely true. But maybe Mulders personality isn't consistent? Maybe the author himself is an idealist NF and it sometimes creeps into the characters? Mulder is more than possible an INTP, according to behaviouristic MBTI the INTP's look for the truth behind things a whole lot. My argument that Mulder is possibly an F sometimes is the fact that he's such an idealist all the time. Nevertheless he's very rational at times. But INTP would be a good description I think... A goofy, nerdy, truthseeker One of my favourite characters of all time. Another argument for a feeler is that he's so VASTLY abstract most of the time, very much like an INFP I know.
Mightier than the tread of marching armies is the power of an idea whose time has come
I agree with Lenore Thompson (Personality Type) who types Mulder INTJ (dominant function IN) and Scully ENTJ (dominant function skeptical ET), using her auxiliary IN more toward the end of the series when she “replaces” Mulder and ends up with an STJ partner even more skeptical than she was. “Spooky” Mulder is a dominant IN (“weird” theories and imagination). IT logic (INTP's dominant function) just doesn’t fit as Mulder’s primary viewpoint. Plus he’s very single-minded in pursuit of his vision of “The Truth”, totally within INJ character. INJs can get very immersed in IN and lose touch with their secondary ET organzing function, which explains Mulder’s messy office.