In working with problems, Rationals try to find solutions that have application in the real world, but they are even more interested in the abstract concepts involved, the fundamental principles or natural laws that underlie the particular case. And they are completely pragmatic about their ways and means of achieving their ends. Rationals don't care about being politically correct. They are interested in the most efficient solutions possible, and will listen to anyone who has something useful to teach them, while disregarding any authority or customary procedure that wastes time and resources.
They are rigorously logical and fiercely independent in their thinking -- are indeed skeptical of all ideas, even their own -- and they believe they can overcome any obstacle with their will power. Often they are seen as cold and distant, but this is really the absorbed concentration they give to whatever problem they're working on. Whether designing a skyscraper or an experiment, developing a theory or a prototype technology, building an aircraft, a corporation, or a strategic alliance, Rationals value intelligence, in themselves and others, and they pride themselves on the ingenuity they bring to their problem solving.
Rationals are very scarce, comprising as little as 5 to 10 percent of the population. But because of their drive to unlock the secrets of nature, and to develop new technologies, they have done much to shape our world.
Although all Rationals share core characteristics, not all of them are the same. In Keirsey's observations, he noted that there were four kinds of Rationals. They are: the Rational Fieldmarshal (ENTJ), Rational Mastermind (INTJ), Rational Inventor (ENTP), and Rational Architect (INTP).
Fieldmarshals will usually rise to positions of responsibility and enjoy being executives. They are tireless in their devotion to their jobs and can easily block out other areas of life for the sake of their work. Superb administrators in any field - medicine, law, business, education, government, the military - Fieldmarshals organize their units into smooth-functioning systems, planning in advance, keeping both short-term and long-range objectives well in mind.
Masterminds are head and shoulders above all the rest in contingency planning. Complex operations involve many steps or stages, one following another in a necessary progression, and Masterminds are naturally able to grasp how each one leads to the next, and to prepare alternatives for difficulties that are likely to arise any step of the way. Trying to anticipate every contingency, Masterminds never set off on their current project without a Plan A firmly in mind, but they are always prepared to switch to Plan B or C or D if need be.
Inventors begin building gadgets and mechanisms as young children, and never really stop, though as adults they will turn their inventiveness to many kinds of organizations, social as well as mechanical. There aren't many Inventors, say about two percent of the population, but they have great impact on our everyday lives. With their innovative, entrepreneurial spirit, Inventors are always on the lookout for a better way, always eyeing new projects, new enterprises, new processes.
Architects need not be thought of as only interested in drawing blueprints for buildings or roads or bridges. They are the master designers of all kinds of theoretical systems, including school curricula, corporate strategies, and new technologies. For Architects, the world exists primarily to be analyzed, understood, explained - and re-designed. External reality in itself is unimportant, little more than raw material to be organized into structural models.