Because Jungian typology is related to how individuals process information & where they start from, what helps them integrate, where it ends, we will judge Tyler's cognitive function using how he starts, integrates, and ends processing at various situations. Then I will proceed to refute popular claim(s) against him, explaining how different the processing could have been. We will pick up key and defining situations to not run indefinite duration of investigation. Long story short, in summary he appears to come closest to ENTP type. Intuition for perceiving underlying meaning and potential of objects, extroverted for using the same intuition to perceive the potential or alternatives in object themselves instead of making coherent impression of such themes in singular form, and auxiliary introverted thinking for explaining or aiding his perceptions through internally coherent logical framings, meaning logic are accepted or made sense of as per how they fit the existing understanding, instead of adjusting to objective factor. First situation, when the narrator meets Tyler Durden for the first time on aeroplane. There are three moments in it including his comment on flight safety magazines he mocks, being direct with the narrator, and sharing about what he does. For the safety magazine, he mocks the shown procedure depiction in magazine calling smiling people in art as "calm Hindu cows", in an effort to uncover his perception of how people try to cope with inevitable and safety. Then following it he explains his understanding of why oxygen masks are dropped, as he puts and I quote, "Oxygen gets you high." Similarly, he asks directly to narrator if he was asking about Tyler's occupation just to "act like he is interested", questioning the underlying reason for why narrator is asking so for no apparent reason (for Tyler at least). When explaining that he is a soap salesman, he explains how soap can serve as an alternative utility to make explosives, followed by the fact about orange juice and kerosene making napalm. These three situations show how Tyler perceives the underlying meaning behind everything, be it the ideal faces on magazine, motive of narrator to small talk, or even explaining interesting alternative to treat basic household items in. This is extroverted intuition seeking deeper utility and meaning behind what senses could directly register in raw form. And he uses introverted thinking to justify why his interpretations make sense, but in subjective form. For instance its not that oxygen literally gets people high, but as per his observation, that's the effect it had on people that fit into his large framework. Second situation, the narrator meets Tyler after his apartment is blown up. Narrator expresses his sorrow and sense of identity loss after his material possessions were lost. How did Tyler respond? Tyler picks an example first as an analogy to explain why narrator mustn't care. He asks, "What a duvet is for? Is it necessary for us in hunter-gatherer sense? If not, then why people like you and me know what duvet is?" Then to conclude further what he is trying to imply he says, "The things you own, end up owning you." These aren't purely logical questions to evaluate and find answers, they instead force viewers to perceive and think of possibilities, multiple interpretations. For example, our properties don't literally "own us", but the underlying essence is that people get attached to their possessions so much that it "appears" as if the possessions own people actually. While logically causal chains would provide thorough reason for what exactly is the theory, extroverted intuition as Tyler used, observes the underlying meaning. Its the way how intuition registers perceptions, unlike sensing's direct perception of how something was sensed. Also its worth noting how his introverted sensing stays largely unconscious and repressed. Instead of recalling how he is still fine, most people still grow, people find solutions, and mankind thrives on evolution, which would be a form of comparing past sensory experiences with new objects, he instead sticks to what alternatives and real-world potentials he perceives, and sticks to them while suppressing what his senses have already registered. This might look biased outward to audience. Many people also type him as ESTP. But the problem is that they use extroverted sensing to process the objects. Perceiving it and orienting around external factor to adjust to constantly changing sensory stimulus, and introverted thinking aids it in integrating internal subjective factor. So an ESTP Tyler wouldn't have tried to find deeper underlying themes, meanings, symbols, or trajectories. Instead he would have taken real-time experiences as the ultimate truth, and used internal logical correctness to justify or further refine his experiences. While our actual Tyler Durden starts processing by perceiving the underlying meaning and then logically justifying them. While other claims like ENFJ and INTJ drift further. Because ENFJ leads with orientation around external emotional fields, while Tyler was not purely or always an emotional influences. He perceived the underlying meaning and forced people to question what they have been taught throughout their life (inferior Si). While introverted intuition keep refining their subjective perception of meaning, and integrate newer observations into the singular impression that conclude to one reality/truth/meaning.