When reading type descriptions, remember that "type portraits" can never accurately describe all people of a given type. Descriptions and portraits like these can only describe the types as they typically are.
ISTJs are methodical and conscientious thinkers who care tremendously about quality and examining things in depth. They tend to critically observe and inspect the things in their environment in order to see whether things and facts add up. When they don’t, ISTJs are often able to put their finger on exactly where and why something is fishy in a way that is not entirely unlike that of a master detective or examiner. For this reason, ISTJs frequently end up in positions of leadership, where they tend to pay special attention to long-term goals, quality control, proper procedures, and accountability.
ISTJs typically excel at keeping track of large amounts of real-world information, and many do well in politics, business, finance or empirical science. They tend to make sure that each piece of information that has been admitted into their internal data library has been cross-checked and scrutinized in depth, so that their analyses will be all the better for it.
For the same reason, they are perhaps the least hasty of all the types when it comes to flinging out loose thoughts and associations about the world. ISTJs tend to prefer the sure and steady approach, building up to the larger analysis by adding data piece by piece, so that as much information as possible has been taken into account before the final conjecture is voiced.
ISTJs rarely set out to become experts within their field. Rather, they tend to set about studying it in order to acquire a full understanding of it themselves and then inadvertently become experts – sometimes much to their own surprise – when it turns out that their standards required them to attain a greater degree of mastery than almost everyone else within their field. They can often be quite humble in this manner, not bragging or being outspoken about their abilities, but preferring simply to let them shine through in their actions.
In their personal lives, ISTJs may sometimes be perceived as a bit unemotional and reserved by others. Even when they are not to conduct a professional analysis, ISTJs nevertheless tend to find that their attention naturally gravitates towards the provable facts of a matter, while regarding plausible-but-airy ideas about the matter, or people’s emotions concerning it, as being secondary in importance. They prefer to be straight about the facts of the matter straight before moving on to less verifiable aspects of it.
Since ISTJs tend to be more serious and task-oriented than most other types, they can sometimes feel a bit unsure about how they should relate to others. They often try to small-talk with others about everyday events in an attempt to appear personable, but at the end of the day, they are often more interested in turning knowledge about events into tasks and challenges that can be solved for long-term gain. Many ISTJs therefore find it easier to relate to people in work or professional contexts, where there is a job to be done, than just socializing or "hanging out," where the rules are more unclear. On the other hand, once an ISTJ knows that the other person doesn’t need them to act in a certain way, they can more often relax and let their enthusiasm and very personal sense of humor guide them in their relations. When this happens, they can frequently make quite interesting and unique conversationalists.
While ISTJs also tend to have a more feeling-oriented and emotional side, they tend to keep this side of themselves under wraps while around most people, and to only express it indirectly, for example, through working to preserve an inner sense of harmony between their own values and the people closest to them. Maintaining loyalty and order in their social circle is thus not just a matter of efficiency or logic, but also a way for them to express commitment to their values and loved ones. They may find it a struggle to express what they are feeling at times, and they don’t particularly like doing so, but their knack for picking up on and remembering facts often serves them well in anticipating and understanding the needs of others. While not people persons as such, they can nevertheless be very loyal and committed in this manner, when their friends and loved ones are going through a rough patch.