ISTJ Primary Function: Understanding the ISTJs Introverted Sensing (Si)

Understanding the primary function of each personality type certainly helps give a better idea of how they respond to and take in information. Their dominant function is definitely going to be what stands out the most and is represented to the world around them. While the dominant function works in combination with your other functions, it is still the one which helps people signify your personality and is often what is presented outwardly. It is definitely the lead function in making decisions and in helping to form a strong sense of self. While understanding all of the functions and how they work together is truly important, knowing someone’s primary function is certainly the first step to knowing them a bit better.

ISTJs are often very practical and driven people, striving to accomplish their goals and get things done efficiently. They can seem to themselves at times, but also are capable of being a member of the community and do their best to provide value for others. ISTJs care deeply about being precise and getting things done right, rather than allowing emotions to cloud their judgement. While their dominant function is their introverted sensing, they have other functions which also play an important role in how they perceive and respond to the world around them. It is certainly helpful to dive into understanding the role their dominant function plays in their lives, but also important to take a closer look at their other functions in order to properly understand the ISTJ and how they are likely to present themselves to others.

How Si Works

Introverted sensing or Si is very much focused on past events and information. It is a way of processing and storing information from past experiences and using it to understand the present choices which need to be made. The Si dominant user will take in information and filter this through their memories, wanting to compare it to past experiences and things they have a better natural grasp on because they have been through it before. When things in the present do not match what they know about the past, the introverted sensing user wants to compare this further and understand what is not matching up right. If they have stored certain information and recognize that it isn’t aligning with something from the present, they often realize that something is not right and needs to be adjusted. The Si user is excellent at recalling the past in great detail, especially things which truly matter to them. This is why they are often good at remembering dates or special occasions, not wanting to forget something which marks and important occasion to them or their loved ones. 

Dominant Si users can sometimes appear methodical, very focused on the details and wanting to be sure they are making the right choices. They don’t like jumping into things without being certain about their actions, and will take time to compare to the past and what has worked for them. This is why new situations can be a bit unnerving for them at times, since they don’t have much to compare these actions to. They don’t like stepping into things blind and want some means of knowing that they are making the right decisions along the way. This way of thinking does make the introverted sensor very practical, wanting to focus on processes and proven methods rather than imagining scenarios which are unlikely to ever happen to them. 

Si in ISTJs

Introverted sensing in the ISTJ personality often causes them to appear rather practical and to the point. They look to the past to make future choices, wanting to be sure of their actions before moving forward. They don’t just jump into new things without taking time to understand what they are doing, in hopes of avoiding mistakes. They can certainly be perfectionists when it comes to things which are important to them, not wanting to feel as if they have failed in some way. Their Si does make them appear closed off at times, but they are simply wanting to take the time to be sure of their choices and actions. ISTJs don’t believe in diving into things by following their emotions, instead they believe in using their minds. They are not at all afraid of taking action, they simply wait for the right moment and the right path to follow. They truly care about doing things the right way, rather than wasting and expending energy getting things wrong and needing to adjust to those errors. This is why they  aren’t interested in taking foolish risks, instead they strategically plan things out in order to be efficient at whatever they strive to do. Their Si is something which helps them to ensure they are following the previous patterns accordingly, cataloging information and important data over time.

ISTJ Functions

The ISTJs dominant Si is important to them, but their auxiliary function is actually what shows most outwardly to the world. This is because their secondary or auxiliary function is the ISTJ extraverted thinking (Te), which is more expressed as it is an extraverted function. This is what drives them towards efficiency and ensuring that they are doing things correctly no matter what. Without the use of their Te the ISTJ would not be quite so direct and capable of taking action. While their Si processes information from past situations, their Te is what helps them follow through with those conclusions. This function helps them to make faster decisions in the moment, going with what is most logical and what they see to be true. It helps the ISTJ be more driven and capable of taking charge of a situation if they need to. This Te works to support the introverted sensing and the many pieces of information that the ISTJ gathers over time. This is certainly what people notice most about the ISTJ at first glance, which is why understanding their functions on a deeper level helps to see what makes them tick.


This Post is Brought To You By BetterHelp


Are you tired of fighting your demons?


Do you feel alone in your internal struggle? 


Do you want to be heard?


Maybe your mental health needs a checkup…


Do you wish someone was in your corner coaching you, 


supporting you, 


and helping you navigate life better?


We have the solution.




You’ve probably heard of BetterHelp on podcasts, TV, or through endorsements from your favorite celebrities. 


The reason it is so popular is because it works. 


Plain and simple.


And that’s why we have BetterHelp as our sponsor.


BetterHelp matches you with a professional therapist that helps you talk through and solve your problems.


You’d be surprised at how much of a relief it is to have someone fighting in your corner to put you back on track and ease your feelings of anxiety. 


Imagine having someone you can talk to weekly about all that you’re struggling with. 


There’s no shame in getting help. 


More and more people are turning to online therapy from the comfort of their own home. 


It’s easy. 


It works.


Picture yourself talking over text or video to a therapist that has been trained in just the right way to handle the problems in your life.


The burden doesn’t have to all be on you. Figure out a way to ease the burden and feel a weight being lifted off your shoulders.


Isn’t that something you want?


We all do. I’ve been a member for more than 2 years and have seen a drastic increase in my mental health and the weight of my inner struggles has definitely been lifted.


Give it a try. I know you’ll be impressed and see results that put you in a better mood and a better frame of mind.


Sign up below and receive 15% off your first month.


BetterHelp: Get 15% Off


Please note: We receive a commission on the sale of any product or service through BetterHelp.


P.S. The 15% Discount is only available through our link here. Sign up for less than $70/week.