ISTJs have tremendous respect for facts. They hold a tremendous store of facts within themselves, which they have gathered through their Sensing preference. They may have difficulty understanding a theory or idea which is different from their own perspective. However, if they are shown the importance or relevance of the idea by someone whom they respect or care about, the idea becomes a fact, which the ISTJ will internalize and support. Once the ISTJ supports a cause or idea, he or she will stop at no lengths to ensure that they are doing their duty of giving support where support is needed.
The ISTJ will work for long periods of time and put tremendous amounts of energy into doing any task which they see as important to fulfilling a goal. However, they will resist putting energy into things which don't make sense to them, or for which they can't see a practical application. They prefer to work alone, but work well in teams when the situation demands it. They like to be accountable for their actions, and enjoy being in positions of authority. The ISTJ has little use for theory or abstract thinking, unless the practical application is clear.