I adapted the following insights from Lenore Thompson’s Personality Type book. If you wish to learn more, I recommend it as an excellent, in-depth resource with far more insights than alluded to here.
Si perceives data by selectively packaging sensations and taking them with the ISJ in the form of facts they retain over time. It helps the ISJ reconcile new impressions with previously stored ones. ISJs are at the mercy of their immediate perceptions, but may not realize this. They are constantly absorbing new impressions, but are sorting through them one at a time, putting them in various “meaning” boxes” set up in their internal storage system.
When facing a decision, or accumulating experiences or information, ISJs examine every fact from every angle, trying to figure out which box it belongs in or whether it needs a new one. They do this with all the facts involved before drawing conclusions. If forced to a premature decision, they will continue to think of things that didn’t occur to them earlier. But if decided on a change, the ISJ is impossible to dissuade. It has become part of who they are, and they want full control over it.
If Se helps an SP keep pace with their imediate sensory impressions, allowing them to “lose themselves” in whatever is happening and become a part of it, Si stabilizes immediate sensations by integrating them with ones the SJ remembers and cares about. ISJs “find themselves” in whatever is happening, because former knowledge anchors their perceptions.
Si accumulates information (facts, names, dates, numbers, statistics, references, guidelines, etc) related to the things that matter to the ISJ. These facts are highly selective and more than just information—they are part of self-experience. They define the ISJ’s specific passions and interests. For ISJs, selective learning is the prism through which they see reality. What is happening now has no stable meaning; to the mind of an ISJ, it is commitments and priorities that give circumstances enduring significance. Knowing what “works” guides them into determining what is worth “keeping.” It gives the ISJ a sense of stability and direction.
ISJs have a strong, lasting personal investment in information that strikes them as important, and their behaviors reflect what they care most about, and what they know is useful and directly related to their specific interests. They pursue these interests so intensely, they may develop into an “expert” before they know it, due to their strong attentiveness to any details that hold fascination for them (and the more they can learn about what they love, the better).
ISJs adapt external situations so well to their own interests that it becomes a tailored expression of who they are. They devote themselves to their particular hobbies or professions, and it becomes part of their social identity. What they are doing consumes them and every detail absorbs them. They work myopically and methodically.
Though often grouped together with the ESJs, they are far different. ESJs have a rational, managing approach to life. They use Si to support and identify with the social institutions that value their rational skills. They value their professional and social roles, and may ignore or regulate activities that conflict with their external responsibilities to “leisure time.” ESJs adjust their pace as necessary to deal with change, and do not attempt to maintain a particular set of rules.
By contrast, ISJs have an experiential approach to life. They focus on the facts and knowledge they possess about what matters to them. They use Fe or Te to rationally manage and prioritize their relationships. For example, ISFJs are constantly alert to others’ practical needs. ISTJs notice others’ needs for logical management and principled council.
ISJs unconditionally maintain their priorities, which stabilizes their reality. They develop specific forms of behavior to keep faith with these priorities. They know how things are supposed to work in areas of personal interest and want to maintain those standards. They have firm ideas of “how things should be” and can be inflexible without auxiliary development, which helps them adjust to shifting circumstances. In extreme cases, ISJs can be championing interests or causes that no longer hold the public’s fascination. Without auxiliary development, the ISJ feels responsible for keeping things “under control” and does not check in with the outside world to determine the relevance of their input to society.
ISJs have an individual way of looking at life, but rarely believe their way of seeing it is unusual. It almost never occurs to them that their views are idiosyncratic, much less unique to themselves. This is most evident in their hobbies and collections—meticulously built and specific to their interests.
They also love to collect variations on a particular experience. Outsiders may not understand the deep, even romantic attachment the ISJ has to certain kinds of objects, information, places, and experiences. Because of their involvement in adjusting outward reality to fit their self-experience, ISJs can struggle to understand that others don’t see reality in the same terms they do. They may think any decent person should see things in those terms. Their response is to establish an area of expertise and exert control over it, as a way of managing the outside world and keeping themselves in a comfortable place.
ISJs often take on too much out of a sense of duty. It’s helpful for them to step outside areas in which they are “needed” to gain helpful extroverted experiences. Without inferior Ne development, ISJs get the idea that any suggested changes to their worldview, situation, or beliefs require them to compromise their integrity. They suspect those responsible for bringing those ideas to the table lack a sense of values or discipline. Furthermore, they may fear that accepting change will cause the whole delicate structure of their worldview to collapse. In these cases, Fe or Te development helps the ISJ focus on the greater impact their resistance causes—on their relationships or their professionalism.
ISJs who resist extroverted functional development find it impossible to consider others’ views. They know they are right and get incensed over suggestions to the contrary. They may become convinced they are the only decent, moral, or responsible person in the situation, and fail to recognize that their perceptions and priorities are subjective.
It takes a lot of work before the ISJ can realize they can adapt to external considerations without betraying their virtues. These ISJs increase the range of their opinions and their capacity for empathy. They radiate a quiet calm but also a sense of authority. They know themselves and their direction in life, but can listen to and accommodate others.
Though similar in some ways in their sense of duty, ISTJs and ISFJs differ in their focus and priorities.
ISTJs are extremely task-oriented and conscientious in handling details. They are unparalleled realists who relate to the facts about external reality (words, numbers, schemes, diagrams, methods, and codes of conduct). They have an extraordinary capacity for details in areas they find important, with unparalleled levels of concentration. They prefer to work uninterrupted and do not mind the tedium of getting something factually and detail-heavy “right.” They are scrupulously responsible and take their authority seriously, but can also be seen as demanding or emotionally distant. They don’t always understand what others want or need and may be uncomfortable or awkward about conveying their warmth.
ISTJs observe the world with a detached sense of irony, and their observations about how it differs from their sensory expectations are both funny and pointed. Due to their responsible nature and reluctance to implement change until having considered all its ramifications, they can be seen by other type as overly cautious or workaholics.
ISTJs are masters of gradual modifications, tinkering with a system long enough until it becomes a streamlined and efficient process—but it may work overly well for them, and not be something easily passed along to the next person in the job, since it is tailored to their specific needs and priorities. They struggle to limit their desire for data without Te development. Left lost in Si seeking of details, they may feel they never have enough information to make a decision, and be cautious about any commitments that require a sustained emotional investment.
Criticism or rejection can badly hurt an ISTJ. They have a strong need to feel valued, appreciated and useful. Someone questioning their honor, word, expertise, or experience can insult them, causing them to become distant. Since they loathe losing control, ISTJs guard their emotions. They want to master a situation through practical expertise and knowledge, and not be reliant upon the whims of their emotions. They judge whether to pursue a friendship by the way that person talks about a common interest. This often tells them exactly who that person is.
Without extroverted development, ISTJs can forget to relate their unqiue perceptions to others’ needs and expectations. This can make them rigid and inflexible, positive about the importance of their opinions and inclined to refuse adapting to the outside world. Instead, they try and control it and force it to adapt to their own needs.
Mature ISTJs realize their way of seeing the world is unique to themselves. They feel no need to prove themselves, or insist others live the way they do.
ISFJs focus their time and efforts on other people, as champions of their causes and with a focus on helping them in a tangible way. They are highly alert to the behaviors and gestures that suggest others’ emotional needs or expectations, and gather experiences that allow them to be of service. They tend to personalize what they do, and focus on others’ goals and needs more than their own. They need to feel needed and have trouble saying no. They need positive feedback and want someone to value their efforts. But their dependability often makes others take them for granted.
Most ISFJs attract those that need them wherever they go, due to their natural sense of empathy, warmth, and friendliness. They will go out of their way to assist others and are sure they are doing the right thing. They are firm and decisive when focused on another person’s needs, but in a group they can be indecisive until knowing how the choices impact every person involved. Others may pressure them to make a decision before they feel prepared, leading them to frustration. Their detail-focus makes them want to make a careful decision, having weighed all options and gathered all facts, but their Fe wants to please others and not “hold up” the group.
ISFJs struggle between a need to be true to themselves and their desire to maintain harmony with others. Because they are so sensitive toward rejection, unsympathetic responses or attacks on their opinions or thoughts may wound the ISFJ, causing them to refrain from sharing their future opinions; they may perceive their ideas and thoughts as “not good enough.” They devote so much time to others, they struggle to find time for themselves. They over-commit, over-produce, and are constant “doers.” Highly family-focused, and generous, they may suffer feelings of resentment at being “used.”
ISFJs may over-prepare in an effort to control a situation. They may develop strong views on appropriate behaviors, manners, or appearances, and judge others according to their personal standards. They need a clear, concrete understanding of what others expect of them. Once knowing that, they will meet all those expectations, sometimes to excess.
Familiarity with a situation may cause the ISFJ to stay in it too long, which is how they wind up in unequal or unpleasant relationships or workplaces. It has become something they are “accustomed to,” it is “how things are,” and it does not occur to them to change it. The ISFJ needs to learn to self-analyze and discern their own needs and goals, and not just focus on analyzing, defining, and meeting others’ needs. Without doing this, the ISFJ becomes locked into certain situations or beliefs that prevent them from personal growth. They can use this to avoid real intimacy or challenging themselves to gain more life experiences.
Once ISFJs embrace functional development, they learn to value their own needs and wants in addition to their concern for others, enabling them to maintain a life of activity without draining their emotional resources.