INTP - or any other type,
is not a personality.
The 16 personality types are a MBTI idea, you can just disregard that.
The four letter codes, are in this instance borrowed just as a system of nomenclature for certain arrangements of cognitive functions.
Type, in this case, means your cognitive function hierarchy, from dominant to inferior.
Inherently, any type has access to their feeling, thinking, sensing and intuitive functions, despite what the 4 letter code looks like. The difference is only in the hierarchy of their ordering.
The hierarchy shows the order in which you'd, under ideal conditions inherently* prefer to use your functions as well as the most probable linear course of development and usage that is expected for any type.
Dominant - Auxiliary - Tertiary - Inferior
However, the functions do not exist as separate elements, they interact constantly, which they in fact have to do, otherwise they would have no productive functionality.
The individual begins from the dominant, which resides as the most prominent part of the psyche, and uses the dominant to access other processes further down the line. Sometimes, so it happens the dominant will rather join the forces with the Tertiary rather than the Auxiliary, sometimes the Inferior will come into play in order to satisfy the demands of the environment before it's time.
Humans are not static, neither is their psyche, a fixed pattern exist (cognitive hierarchy), but it's inner workings are flexible.
I'll illustrate it with a metaphor.
That is, the underlying cognitive constitution of an individual.
A phenotype is any observable characteristic or trait of an organism: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior. Phenotypes result from the expression of an organism's genes as well as the influence of environmental factors and the interactions between the two.
Personality is a product, the emergent traits, behaviors that manifest in an individual as a result of interaction not only of their functions but a huge number of influencing factors and stimuli we are exposed to every second of our lives that shape and prompt us.
There are no 16 personalities on the planet, but there are 16 distinct patterns that their individual personalities can be traced back to.
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* There is some argument over what exactly makes such and such functional ordering inherent for an individual. It is often explained by the fact that they are the most energy efficient in a physiological and consequently psychological sense. There is some research to confirm this, but it is not conclusive yet.