Understanding Introverted Sensing, The INFJ’s “Demon” Function

If you are an INFJ, you may have wondered why you can’t remember what happened at the work party you went to only a week ago, or why your laundry piles up when you have a new idea and you’re glued to your computer writing about it. This happens because our imagination and future focus are at the center of our being, and our intuitive process is always moving towards possibilities.

You probably know that you’re an Intuitive (as opposed to a Sensor). Taking in information with our senses is not the INFJ’s cup of tea, and our connection to the concrete world of reality is often weak as a result. We prefer our inner world of insights to lead the way.

But sometimes, if we completely ignore our Sensing function, it comes back to bite us. To understand what this means, let’s look at how Sensing operates for INFJs, and especially Introverted Sensing, the hidden “demon” that tries to undermine us.

Sensing vs Intuition as Cognitive Functions

Cognitive functions are the specific mental processes that determine an individual's psychological type and how they interact with the world. They focus on how we either gather information (Sensing/Intuition) or make decisions (Thinking/Feeling).

You can think of the Intuition and Sensing functions as the “lenses” through which we view reality:

• Sensing: Focuses on the present moment and physical reality. You rely on your five senses to gather concrete facts, data and lived experiences. It’s about “what is.”
• Intuition: Focuses on possibilities, patterns and future potential. You rely on gut feelings and connections between ideas. It’s about “what could be.”

In Jungian theory, these functions are either oriented outward or inward. If a function is Extraverted, it means you use your Sensing or Intuition to engage with the physical world around you right now, while Introversion means you use them to explore the ideas and memories inside your own head.  So, no individual just “Senses”—you either Sense the world around you in the present (Se) or you Sense your internal library of memories from the past (Si). 

Extraverted Sensing, the INFJ’s Inferior Function

As an INFJ, your inferior function is Extraverted Sensing (Se). Se occupies the fourth place in your function stack, and it is your most challenging conscious mental process. “Conscious” in this context means the mental processes you can actually “feel” yourself using and can control with purpose, much like being aware of your own hands while you work.  

For INFJs, Se is responsible for our observation skills, which are honed when we need them to build a foundation for our insights. As all functions operate in service to our most preferred function, Introverted Intuition (Ni), Se grants us a platform from which to launch our abstract ideas. INFJs use Se to gather concrete data for pattern recognition that’s powered by Ni.   

But these concrete details land on us more as “impressions” than as “facts.” This is because our dominant Ni is always connecting the dots to create a pattern of meaning. Se provides the details, but Ni instantly assembles them into a big picture and lingers there. This is why INFJs will not stay focused on the external present for long.

This can be understood by looking at the INFJ’s appreciation for art. While we might engage the aesthetics of a painted masterpiece with intensity, the sensory experience is often short-lived and is just the beginning for us. After we take in what we see on the canvas, we automatically and naturally dive into our irresistible Ni universe looking for meaning and deeper ways to understand what we saw.

There is a reason we only dabble in the use of Se. We need it for stability and input, but only as long as it takes to propel us into our inner world of Ni, our home and superpower. 

Introverted Sensing, the Demon Function of the INFJ

Remember I said that Sensing can be oriented inward or outward? The inward version of Sensing is Introverted Sensing (Si). Those who use it in a healthy way have access to concrete facts from the past. They’re like filing machines—they store detailed memories about what worked before, and Si helps them discern which details should be retained to be used later. Since Si is introverted, it works with subjective data, preserving what is true and important in the value system of the user.

But when we look at the value system of the INFJ, we see that it relies on intuition, creativity and new ideas produced by Ni, which is the exact opposite of Si’s look backward at past experiences and proven facts. This collision of values drives Si into the darkest corners of our minds. There, it’s so deeply buried in our unconscious that most of us don’t even know it exists. In fact, Si sits in the 8th position of our function stack. Yep, that’s the very last one. 

There are eight functions in total, and the functions that sit in places 5-8 are called shadow functions. Unlike our conscious functions, they are the lowest, most “hidden” parts of our mind that operate automatically without our permission, usually showing up as impulsive reactions or weird behaviors when we are under a lot of pressure. Si is the very last of this unconscious bunch. And the more unaware of Si we are, the more emotionally dangerous and inaccessible Si becomes. This is why we call it the Demon Function of the INFJ.

To summarize what’s happening here, the inner world of the INFJ is at great odds with Si for three reasons:

1. Our personality is future-oriented and drawn to possibilities that will improve the world and add depth to our experiences. Looking back is not natural to us.
2. Our powerful Introverted Intuition (Ni) has us fully immersed in its mysterious adventures. We’re often not present (not aware) in the real world, miss what’s going on in our environment and can’t remember it later.
3. The physical world is not a big part of our value system. We don’t usually care about the shiny things we see and soon forget them.

How Does Si Manifest in the INFJ?

When we ignore a part of your brain for too long (like our Si), it doesn't just go away—it turns sour and starts acting out behind our back. So, instead of being a helpful tool that remembers where you put your keys, it becomes a demon that hijacks your brain and forces you to feel miserable or act in ways you can't control. For example:

• You dismiss helpful details from your past as “trivial” and miss any lessons you might have learned from them. 
• You might ignore your physical body because you haven’t set up healthy habits and routines to take care of yourself. 
• When you reminisce about the past, you might get stuck obsessing over a tiny mistake you made 10 years ago. I believe that rumination is the most harmful effect of Demon Si, because it can come in the form of an insidious attack on your self-worth. 

How to Integrate Introverted Sensing

We must remember that all 8 of Carl Jung’s cognitive functions, both the conscious and the shadow functions, should be integrated for quality mental health. But I have to tell you that not everyone thinks you should spend time trying to improve this part of your personality.  There are those who say, “don’t bother,” because it’s just too difficult!

But I say yes, we INFJs should go there, because when we attempt to integrate this demon, we automatically bring it into our awareness, and that’s more than half the battle. Even if we are not successful in using it, we can lessen its power over us by seeing it.

Remember, practicing Si will not be as simple as using other functions. Don’t think you’ll fix it with a little yoga and a bit of journaling, although those are great for any problem! But Si is the big dog, the leader of the pack when it comes to INFJ darkness and destruction, so we will need to become INFJ warriors to even bring it into view, and then make it a more useful, positive process under your control.

Try these six ways of engaging Si. They will help you identify the unhealthy ways it manifests in your personality:

1. Learn to recognize your Si Demon function.

For the most part, Si is buried so deep in the INFJ psyche that it doesn’t pop up until we are stressed. Learn in advance what this looks like for you—are you overthinking the pain from your past?  Have you been completely neglecting your body? These awful states of mind may be the result of Si acting up below your level of awareness. Recognize your own brand of Si misery and when it comes simply say, “I see you.”

2. Use Ni as your safeguard.

There’s a reason we call Si our “Demon.” Expect to feel discouraged sometimes. But don’t let this devil destroy the positivity provided by Ni, because you can tap into your dominant function at any moment—it’s always there as your guardian, your defender, your chief support. Allow this foundational mental process to be your cornerstone as it brings safety in the face of past experiences that Si will use against you.

3. Build a connection with your past experiences.

Connecting with details of past sensory experiences doesn’t come naturally to the INFJ. To do this, you may need help with prompts like sentimental objects or pictures. As you recall events, focus on any positive emotions you felt, even if the overall memory was a bad one. For example, if you experienced the devastating death of a loved one, try to identify something positive about it. Was there someone there for you offering love and support, helping you carry the weight of the loss? Try replacing the overall sadness with specific, positive aspects you have overlooked.

4. Make new, comforting memories.

Sounds easy at first, but it requires staying in the present moment and creating routines.  Both are hard for the INFJ. Let a routine experience, like a daily walk, become a familiar, positive ritual that you file away in your mind and can access later. This will give you many chances to have new sensory impressions that will shore up a sense of well-being and stability.   Maybe your walks get longer and more intense as your body grows stronger. These kinds of memories bring good feelings of comfort and self-esteem.

5. Use Si as a platform for launching ideas, just like Se.

Use Si to support Ni, just as you use Se as a launching pad for abstract ideas.  You can do this by focusing on concrete experiences from your past, and allowing Ni to instantly create meaning and patterns from those impressions just as you would use the present sensory experiences of Se. Si can enhance Ni by providing reliable solutions from its stored data as it checks Ni against what worked before. This prevents roadblocks as Ni creates your treasured visions, and Si screens them for feasibility. After all, what good are your dreams if they won’t work in real life?     

 6. Observe someone who leads with Si.

If you have encountered someone who leads with Si (an ISFJ or ISTJ), you may have said to yourself, “Who is this alien who can remember each detail of their birthday party at 5 years old? I can’t even remember yesterday!”  Still, if you can get a glimpse of one of these virtual card catalogers in action, take the opportunity to observe how they confidently reach back into their personal history and harvest details that solve problems in the moment. But never expect to do this as well as they do. It’s enough, at least in the beginning, to watch them and develop awareness.

Final Thought

My encouragement to you is that you work on recognizing Si when it pops up unexpectedly, not that you master it.  Recognizing Si is more important than practicing it.  Practicing Si is the icing on the cake, but baking the cake is seeing it. If you are aware of this barely perceptible menace when it comes up to threaten you, consider yourself accomplished. You have overcome the harm that Si can cause to the underdeveloped INFJ who hasn’t yet hunted that Demon, and you have taken the power away from it.