ISFJ, or Introverted Sensing Feeling Judger, is a label borrowed from MBTI nomenclature and now applied to the Jungian Cognitive Function set {Si, Fe, Ti, Ne}.

Dominant: Introverted Sensation (Si)

"It seems so obvious that it's kind of silly I even have to say it, but things just always seem to go more smoothly when you know exactly what you're doing. There's really nothing quite like having your own private map for how to do things--the more I study and work on the areas I'm interested in, the more I develop this ability to connect my experiences to everything else I've done, and the process just builds and builds. I don't even mean for it to happen that way--I guess I just know what kinds of things I like, and I know what makes me comfortable and what doesn't, and I know that the more I plan my life around setting myself up to work in areas I know I'm confident in, the more I'm going to succeed and the more in-depth information I'm going to have about the skills I specialize most in. I think one of my greatest strengths is that I know what I'm good at, and, perhaps even more importantly, I know what I'm not good at, and I have the good sense to know when to avoid the latter. I don't understand why people insist on haphazardly jumping into things they don't have any idea how to handle properly. What's the point? If you don't know what you're doing, aren't you just bound to fail?"

ISFJ is one of the most poorly understood types in the entire Jungian Cognitive Function canon. The fact that they're often misunderstood and inaccurately stereotyped as groveling doormats who live to serve others and let people walk all over them serves only as a testament to the true extent of their humility in terms of how private they keep their true selves and their real passions and interests.

While they do prefer to conduct the bulk of their interactions with the external world through auxiliary Fe (which I'll get to in the next section), that is not at all the primary focus of an ISFJ's cognitive hierarchy or preferred lifestyle. To understand the significance of Si, we need to touch for a moment on the overall nature of introverted perception (Pi) in general, and to compare and contrast it with the extroverted perception attitudes by which most people who have written about ISFJs have gathered their information and totally missed the point of what these people and their dominant attitudes are really all about.

There's a scene in the film Across the Universe where two characters argue over the dinner table about the nature of experience and identity. While one of them, a young P type, argues that, "Who you are determines what you do", the older character (presumably a J type) insists on exactly the opposite: "What you do determines who you are." This latter attitude is a great way to introduce oneself to the philosophy central to Si: we build our identities on the experiences we've internalized. This is fundamentally why Si dominants go to such great lengths to control their experiential intake: they're not turning down unfamiliar experiences just to annoy their ExxP friends; they simply understand that the comfort in perceptual familiarity is such a powerful force in their own lives that they have to be extremely careful not to fill themselves up with too many experiences that might not end up being healthy or productive for them in the long run.

They know themselves well enough to realize that, above all, their natural tendency to seek out very specific kinds of informational and experiential input depends directly on the kinds of input they've become accustomed to through their prior life experiences. Like their Ni dominant cousins, Si dominants are most concerned with how their individual cognitive tendencies associate meaning with various kinds of signs and information; however, since they assign this meaning based on direct association with highly detailed sensory information imprinted on their consciousness from previous associations, they know that if they start spending a lot of time involving themselves in a certain kind of experience, the fact that it becomes familiar and slowly works its way into their experiential comfort zone means they may start to like it. And then they may never stop doing it.

While Pe dominants are constantly on the search for all sorts of new information and new experiences of as many different kinds as they can get their hands on, there's not as much of a threat of becoming attached to any one specific sort of experience or information. They'll just tire of it and look for something new the next day anyway, but not so for Pi dominants: since they have to focus their attention fully and completely on whatever kind of information they're seeking out, they can't just shut off this focus and switch to a different kind of input on a whim. Once they allow themselves to become immersed in the absorption of an experience, they know they won't stop until they've built a completely internalized map of every detail of every piece of meaning this experience has for them. Their choices of experiences literally create their identities--so how can they not be constantly wary of what sorts of experiences they let in?

ISFJs are, above all, highly cognizant of their own impressionable nature. They like to figure out what areas interest them, and then maximize the absorption of all sorts of information, data, skill sets, and experiences related to "mapping" as much of that terrain as humanly possible. I've known ISFJs who sit up all night on Wikipedia reading about their favorite subjects. Note that they don't prefer hopping around to as many different unrelated articles as they can find--they have a focus, a taste for certain particular flavors of input, and they want to know everything they can about those specific areas. If you've ever watched Antiques Road Show, well over half of the expert analysts who appear on that show are likely ISxJ types. They didn't necessarily set out to become experts in their fields--they just found that they so enjoyed internalizing sensory information related to, say, World War II-era Confederate rifles, or Kandinsky paintings from the 1920s, that after focusing their lives on these fascinating pursuits for so long, they eventually found that they'd become certifiable experts. Given enough time to learn, absorb, and practice all the established information, methodology, and techniques in a given area, Si dominants will outperform virtually everyone in terms of consistency and thorough attention to detail.

Auxiliary: Extroverted Feeling (Fe)

"Govern a family as you would cook a small fish--very gently."
--Chinese proverb

Once we move past the dominant and start to focus on the auxiliary, we start to see where the general misunderstandings and assumptions about the ISFJ type originate. Given only knowledge of their public faces, it's relatively easy to assume ISFJs have no internal lives and exist as sort of less effective versions of ESFJs, using Fe as a public interaction method but not commanding it as fluently as their ESFJ brethren.

This is, of course, due to the fact that Fe is only a secondary concern for ISFJs--an important part of their lives but ultimately subservient to their personal quests for experiences associated with the familiar sensations they find most pleasing. In order to form meaningful connections with others and establish any sort of communal framework, it's vital that ISFJs master the objectively verifiable language and methodology of externalized Feeling judgment. As Fe develops, ISFJs will develop important interpersonal skills, along with consistent attention to the needs of their friends, family, and other individuals to whom their connective obligations suggest they share mutual responsibility. This is where the commonly understood impressions of ISFJs as loyal and conscientious group supporters come from: and indeed, when Fe is strongly in place, this awareness will absolutely form a vital component of their total selves. They will work tirelessly to promote the best interests of their loved ones, developing fluency not only with practical day to day maintenance tasks, but with any skill which may contribute to the well-being of others that their culturally supported networks of interpersonal obligations suggest is their responsibility.

All the while, the healthy ISFJ manages to balance this network of familial responsibility against her own personal desire to continue her quest for absorption of ever more information and experiences related to the sorts of sensory input that, over time, come to define her comfort zone. Indeed, Si and Fe should ideally become intertwined and mutually beneficial to each other, as the experiences associated with organizing, encouraging, assisting, and bonding with loved ones help to grant more definite and outwardly observable shape and meaning to her internal mass of undifferentiated experiential input. Fe is vital to the formation of interpersonal networks upon which her fundamental need for consistency and routine (based on a desire for new information to relate concretely to that which has been internalized and understood before) can depend. It grants her not only a means of communicating and defining the significance of her relationships to others, but an ability to depend upon others and show them that she herself can be depended upon as well.

If Fe goes undeveloped and leaves SiTi to handle the majority of cognition, the ISFJ is prone to feelings of terror that his trusted support network will fall out from under him at any given moment. Trusting others to handle important tasks becomes an uneasy endeavor at best. Since the feeling of trust and security upon which Si depends so heavily is never connected in any meaningful way to the bonds and relationships defined by interaction with others, the SiTi loop ISFJ feels that no one but himself can ever be depended upon to bring him the sort of consistently reliable experience his dominant function necessitates that he have access to. Without a way to describe or objectively designate his feelings for others or theirs for him, no sense of faith in upholding mutual responsibilities can form--he must do everything for himself, or risk total ruination through the failure of other less reliable individuals to uphold their agreements and obligations. If you want something done right, you have to do it yourself--or risk facing the unknown, totally unprepared--which, of course, represents Si's worst fear of all.

Tertiary: Introverted Thinking (Ti)

As ISFJs find themselves so singularly focused on developing their internal maps of experiential impressions and defining their directions in life based on the kinds of experiences these maps point them toward, at some point in life it follows that they should begin to ask the question: What if the map is wrong?

Dealing with this possibility is, to Si, unfamiliar (and therefore frightening) enough that most ISFJs defer almost exclusively to Fe in determining the answer: If my impression of how something is has somehow misled me or given me wrong information, surely I can count on the people to whom I hold cultural and familial bonds to remind me that I've lost touch with what our community finds most important. Surely, by listening to the ethical consensus of those to whom I feel closest, I can discover and rectify the problem when my own desires conflict with the institutional customs and values by which my relationships to others are given objective meaning and definition. Unfortunately, however, the savvy ISFJ will invariably notice situations in which neither Si nor Fe seems to offer any reasonable solution. Despite Si's inherent preference for that which has come to define its comfort zone ("If it ain't broke, don't fix it!"), at some point the ISFJ will be forced to evaluate situations in which her community's collectivized ethical norms will strike some part of her being as somehow fundamentally flawed, even if these norms are consistent with the kind of experience she has built into Si's vast internal database as the familiar and consistent standard she has come to trust.

When this happens, the involvement of tertiary Ti enters the picture primarily to serve as a sort of corrective force in the event that something has been written onto the map that may come into conflict with the ISFJ's own innate sense of logical reasoning. "This is what I've always done, and it's what everyone I find important says I should be doing, and yet something about it simply doesn't make sense." This can be doubly disconcerting as it represents not only a break from the unconditional trust the ISFJ normally places in her own self-referential experience, but also a deliberate separation from the outward judgments upon which her relationships to others are most directly verified through external reinforcement. The introduction of Ti into the mix seems to poke holes in the very fabric of everything by which the ISFJ has come to define her own existence--and yet she still can't ignore it. It's only through this vital corrective process, however, that the ISFJ is able to rewrite segments of her own sensory maps to align more closely with a sense of universal fairness and consistency in principle which extends beyond that which her own limited personal experiences with the evaluative standards of her communities have the context or precedent to grasp or define completely.

When applied negatively in a poorly developed state, Ti may cause counterproductive changes as its insistence on "just knowing" that something is (or is not) inherently fair or reasonable can reinforce all of Si's worst tendencies in terms of subjective self-reference as the ideal solution to any and all problems or disagreements. Convinced beyond all doubt that only he has the true depth of experience to understand the problem in realistic terms, the SiTi loop ISFJ may reject any and all outside opinions regardless of the status or relationship implied by the characteristics of the person offering them. "Listen, my wife doesn't know what's best for our children--I'm the one who's been there looking after them from day one!" Neglecting Fe's vital external input can leave the ISFJ lacking any sort of meaningful outside standard against which to weigh his own subjective evaluations of the overall value of any given idea, practice, or methodology.

On the other hand, once Fe has been granted the necessary growth and development time, Ti may step in to assist it with the evaluation process and remind the ISFJ that yes, it is possible for our family and friends to be wrong, and sometimes we need to have the courage to stand up for our own beliefs when faced with decisions that will directly impact our own lives and personal needs. More importantly, Ti allows the aforementioned sort of retroactive "map correction" process by which internalized sensory experience can be questioned, devalued, and ultimately overwritten with more effective and consistent ideals. For the ISFJ, Ti is there primarily to serve as a reminder that his own experiences and impressions do not always equate directly with the mostly universally just or reasonable approach, and that, somewhat paradoxically, sometimes the only person who can make this distinction to the necessary degree is himself.

Inferior: Extroverted iNtuition (Ne)

Last but not least, the Achilles' Heel: many of the typical complaints others have about SJs (and especially ISJs) can be traced to manifestations of inferior Ne. On a surface level, Ne opposes everything Si holds dear and considers vital to maintaining a healthy outlook: while Si would encourage us to find exactly what we're looking for on our internal maps before setting out to find it, Ne takes a somewhat different approach: that the most interesting things in life are usually surprises.

It should be relatively obvious by now that Si doesn't like surprises. It wants complete information and it wants time to sort through every piece of the information given and compare it to the sense of static, internal consistencies by which everything in its worldview is granted stable meaning and significance. Until you can relate a given piece of information to something you already know, until you can show where it would fall on the map you already have, Si not only has no use for it, but is actually threatened by its imposing presence among the already-sorted information by which its identity and worldview are defined. Inferior Ne seems to throw a wrench into that identity itself: By encouraging the ISFJ to ignore what he knows and instead let loose and actually enjoy a constant influx of new and unfamiliar ideas from as many different unconnected sources as possible, Ne seems to attack everything the Si mindset holds as important or meaningful. Rather than carefully compare each nugget of data to every other piece of data we already hold, each new piece of information seems to suggest even more connections to even further-reaching outwardly defined patterns that continue to change the meaning and threaten stable interpretation the more we indulge them.

It's almost as if Ne would suggest that the more we know, the more we don't know; the more we discover, the more we find out is potentially wrong with the map we're reading now. Rather than contribute to a more complete understanding, inferior Ne frightens the ISFJ by telling him that the more he learns, the more he will be forced to deal with the unknown without a plan of action or the opportunity to educate himself on the possible responses. The result is often a form of stalled burn-out, trapped between the desire for knowledge/preparedness and the inevitable realization that the more knowledge he gains in his preferred areas, the more he will have to acknowledge new relationships and connections between that knowledge and other as-of-yet unknown areas. The resultant realization that he will never possess a complete map strikes the ISFJ as a terrifying reality: there will always be uncertainty and there will always be things he has to adapt to without preparation time.

In practice, inferior Ne often manifests itself in the form of outlandish insecurities and fears resulting from the inability to distinguish between the relative probabilities of the occurrence of various events: as the ISFJ becomes more and more stressed, he is forced to confront an uncontrollable flood of increasingly strange and unrealistic possibilities for the future--what if my spouse dies of a heart attack? What if my office is engulfed by a giant fireball? What if aliens enslave Earth and kidnap my children and I never see them again? What if the unrelenting flow of constant future possibilities totally ruins my confidence in any sort of stable or consistent lifestyle--what if I can never count on anything to stay the same again?

Of course, like all inferior functions, Ne can eventually be harnessed for positive use--but it takes a long time and a lot of personal development. When a very well-balanced ISFJ is able to stop viewing Ne as a disturbing threat to his sense of security and perceptive stability, it should actually assist and support dominant Si's desire for more information by granting him new paths and avenues by which to obtain more information of the specific types and categories which he finds so pleasing. He will continue to seek out information and experiences that seem related to that which he's already mapped--that doesn't change--but what does change is his ability to recognize the relationships between seemingly "unrelated" areas of knowledge. He may not even consciously realize he's doing it, but this expanded awareness of the interconnectedness of all knowledge will make the ISFJ feel more comfortable learning and adapting to new contexts than he ever thought possible. Areas in which he has relatively little experience will suddenly seem much more familiar (and therefore less daunting) than they ever have before--he will unconsciously find something in the new area that relates back to something he already knows; by making the unfamiliar seem familiar, he will "limit" his perceptual intake (and thus remain in his comfort zone) while expanding it into all sorts of new directions. He will unwittingly teach himself to improvise through the simple realization that, when we are able to see some form of abstract relationship between any combination of ideas we can imagine, everything seems related in some way or another, and thus all new information can be traced back to that with which he is already well-versed and comfortable.

Exploration in the name of expanding one's comfort zone, so that one never has to leave it--whether or not the self-actualized ISFJ realizes this is what he's doing, it makes his experiences that much more complete, and his life that much more well-rounded and fulfilling.