The Spectrum of Rationality-Irrationality
No dichotomy exists in itself, there are no walls dividing functions in the psyche of a type. A socionics type is a complex system where all parts are interconnected and influence each other.
Let's take a look at how other dichotomies can influence rationality/irrationality.
Ethics is the more labile (changeable/flexible) polarity, and to some extent, it's more irrational. An ethical type's actions are synchronized with the feelings and emotions of others. This makes the rational ethical type more flexible than the rational logical one.
Logic is the more inherently rational polarity. It's tied to the objective essence of the process and cause-and-effect relationships, which makes the logical type inherently more rigid.
The Role of Sensing and Intuition:
Sensing is the more flexible polarity. A sensing type easily adapts to external conditions (introvert) or flexibly modifies them (extravert).
Intuition is the more rigid polarity. Intuitive types tend to be fixated on ideas, imagery, and hypotheses. Their reaction to changes in the environment is more delayed and indirect. Because they are often deep in thought, they might, for instance, miss their subway stop.
The Role of Extraversion and Introversion:
Extraversion is generally more irrational. Extraverted types are more labile (unstable/reactive) because they quickly respond to new information and external stimuli. An extravert skips some steps in processing; their thought process is faster. In a conversation, an extravert quickly incorporates new input.
Introversion is generally more rational. Introverted types are more rigid because they need to correlate new information with existing information. Their response is more delayed. In a conversation, an introvert type needs time to process and establish more connections.
... And this list can go on.
So, what do we do when it seems we don't neatly align with a textbook description, or even find ourselves somewhere in the middle?
We have many tools available that not only help with typing but also provide a better understanding by looking at all these parts from another angle.