By Boye Akinwande
ISTPs and INTPs are dominant introverted thinking types. Whether they have introverted or extroverted thinking, all thinking types tend to have a strong proclivity for impersonal analysis and discerning the mechanics governing phenomena (as opposed to how they feel or appear to our sentiments). However, where the extroverted thinking types orient their analysis externally, taking stock of empirically verifiable facts and standards and letting these inform their thinking so as to come up with expediently realizable plans and predictions of outcomes, introverted thinking works somewhat differently.
The types who have introverted thinking tend to have a more laid-back, explorative approach where the outcome isn’t as important as the process of analysis itself. Furthermore, where extroverted thinking types tend to reply on the empirical facts at hand, introverted thinking types tend to rely more on their own theories about which facts go where in a mental system of their own making. You might say introverted thinking types do not simply trust the facts, but try to circumvent the external world’s many cluttered facts by coming up with overarching ideas to make sense of them instead of engaging with them directly. As Jung said of the introverted thinking type in Psychological Types, to them the facts only function as proof of the idea.
Because the process of reflection is more important to introverted than extroverted thinking types, both ITP types tend to have a knack for understanding how things work in an impartial and detached way. Thus, while they aren’t as outcome-oriented as their extroverted thinking counterparts, they nonetheless tend to excel at flexible reasoning and problem-solving in scenarios where something besides the tried-and-true approach is called for.
If one takes a function-axes approach to typology, as we do on the site, ISTPs and INTPs are alike on their judging axis of dominant introverted thinking and inferior extroverted feeling. Where they differ is with regards to their perception axis: Here ISTPs have auxiliary extroverted sensation and tertiary introverted intuition, whereas INTPs have auxiliary extroverted intuition and tertiary introverted sensation.
Types who have extroverted intuition as one of their top two functions are NPs and types who have extroverted sensation as one of their top two functions are SPs. If we compare the two, SP types tend to be much more immersed in their immediate environment and the natural flow of life than NP types. Their cognition tends to be more drawn towards objects as they exist physically, experiencing them in their entirety and as they are.
For NP types, instead of focusing on objects themselves, they are much more likely to be tempted to chase novel ideational possibilities at every turn than actually remaining with objects in the real world at length. It is like two people walking in a forest, one taking stock of the forest, the paths, beauty, berries and wildlife all around, and another, only partially present in the experience itself, thinking that he at one point saw a cloud with an intricate shape through the canopy and now he can’t wait to get out of the forest to see what the cloud is really like.
That is to say, compared to SP types, NPs are constantly striving to step outside the natural flow of life and its physical and empirical constraints, constantly asking “what other possibilities could the world contain?” With extroverted intuition high in their consciousness, NP types constantly feel a need to escape and transcend the immediate givens of any situation, even if they do not quite know how such an escape could be achieved.
Thus, while all introverted thinking types tend to be detached from fastening to specific outcomes in their thinking, and then reverse engineering the process of reasoning from there, ISTPs are nevertheless drawn to tailoring their analysis in ways that are cognizant of specific real-world goals and outcomes due to the prevalence of extroverted sensation in their consciousness. This leads their cognition back to focusing on the empirical world before things get too ivory tower-like (as they may often do with INTPs).
Compared to INTPs, ISTPs are much more likely to want to derive tangible results from their analyses. Keeping this in mind, it is really no wonder that ISTPs are sometimes stereotyped as the practical problem solvers par excellence.
By contrast, the cognition of INTP types tends not to be as focused on actual objects and physical reality as the ISTP. Nor is the INTP as beholden to achieving specific outcomes as the ISTP. The philosophy of Immanuel Kant, as found in his Critique of Pure Reason, provides as a good example of the INTP’s comparative lack of attention to outcomes: Kant spends a lot of time qualifying human knowledge and pointing out what we can’t know. The work is generally agreed to be impeccably reasoned, but the way forward from his many qualifications and reservations is also agreed to be less clear. Many ISTPs would probably lose their patience with such a perspective, or, even if they enjoyed it, they might regard it as an intellectually fascinating perspective and not a real lived perspective the way an INTP might do. Again we see the INTP being more attuned to pure ideational possibilities while the ISTP is more attuned to direct, first-hand experience drawn from reality itself. And Kant’s philosophy, as even he himself would admit, is plainly at odds with lived experience.
To many ISTPs, such ivory tower-like perspectives tend to be at odds with their reality-focused outlook on life and sense of expediency. As one likely ISTP once said, “If the work is good, what you say about it is usually irrelevant.” From the ISTP’s perspective, we might say that INTPs are in many cases more stimulated by the “talk” than the work. That is, the abstract principles and categorizations INTPs use to understand the work actually dilute the intensity of the singular work in order to reveal a more general, more theoretical picture of how the work relates to other similar works.
 Myers also makes this point in Gifts Differing (Davies-Black Publishing 1995) p. 81.