Definitions.
Type: A solidified unconscious tendency of thought.
Temperament: An aggreggate of unconscious tendencies of thought.
Introversion: An unconscious tendency towards contemplation rather than interaction with the external world.
Extroversion: An unconscious tendency towards interaction with the external world rather than contemplation.
Perception: An unconscious tendency towards observation of the external environment rather than judgment of what has been observed.
Judgment: An unconscious tendency towards assessment of what has been observed.
Sensation: An unconscious tendency towards observation of the external world with our five senses.
Intuition: An unconscious tendency of observation of the external environment by virtue of imagination or abstract perception.
Thinking: An unconscious tendency towards dispassionate assessment of the environment observed.
Feeling: An unconscious tendency towards emotive valuation of the environment observed.
The above defined terms are 'types'.
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If the man in question is an INTJ, his temperament is an aggreggate of Introverted Intuition and Extroverted Thinking. The sequence of the remaining functions is defined by the antithesis of the above functions with other functions. Hence, if Intuition is his dominant function, Sensation must be inferior, if Thinking is moderately favored, Feeling must be moderately disfavored.
If the man in question is an ISTJ, his temperament is an aggreggate of Introverted Sensation and Extroverted Thinking.
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Definitions of temperaments.
Introverted Perception: Observation of the external environment in terms of how the environment relates to the self and not observation of the environment in terms of how it is as a thing in itself. Introverted Sensation and Introverted Intuition are both examples of Introverted Perception.
Note on Introverted Perception: In the case of a temperament where Introverted Perception is prevalent, the environment is fundamental to the inner being of the person in question. That is the case because introverted perception is the most influential introverted function. Therefore this function has the most influence on the inner life of the individual. If the Introverted Perceiver in question is an Introverted Sensor, the physical external environment must be in the condition that the Introverted Sensor deems most favorable. In most cases this means in sanitary conditions and appeasing to the senses in other ways. If the Introverted Perceiver in question is an Introverted Intuitive, he will tend to be more concerned with having the abstract vision of the external environment in adequate conditions. Intuition is by definition antithetical to sensation. Hence, the Introverted Intuitive in question will have little regard for ensuring that the external physical environment is in adequate condition.
For example, Nietzsche and Sartre were clear-cut INTJs who were chiefly concerned with ensuring that their vision of how the world should operate is preserved. They had almost no regard for ensuring that their desk is clean and ordered or that the physical environment they inhabit is in pristine clear conditions. The Introverted Intuitive type almost inevitably is concerned with abstract ideas. This is the case because the dominant Intuitive faculty inevitably engages in imagination or abstract perception. This type inevitably becomes a visionary. An open-minded approach to life is very common among INTJs, simply because their tendency to be a visionary allows them to contemplate many different perspectives. As a result of this, the INTJ is often able to see the situation from many different angles. Creativity, for the reasons mentioned above, tends to be highly valued. For this reason INTJs are over-represented as novelists, scientists and philosophers.
Introverted Sensation: An unconscious tendency towards perception of the external environment by virtue of the five senses.
Introverted Intuition: An unconscious tendency towards perception of the external environment by virtue of imagination.
Another note on Introverted perception.
"Even with only a slight increase in the power of the unconscious, the subjective component of sensation becomes so alive that it almost completely obscures the influence of the object. If the object is a person, he feels completely devalued, while the subject has an illusory conception of reality, which in pathological cases goes so far that he is no longer able to distinguish between the real object and the subjective perceptions....Actually he lives in a mythological world, where men, animals, locomotives, houses, rivers, and mountains appear either as benevolent deities or as malevolent demons. That they appear thus to him never enters his head, though that is just the effect they have on his judgments and actions. He judges and acts as though he had such powers to deal with; but this begins to strike him only when he discovers that his sensations are totally different from reality." Psychological Types.
Because perception of the Introverted perceiving type orients around the subject and not the object, perceptions are easily distorted.
The perceptions of the Introverted Sensing type orient around the external world, or perceptions of what can be observed with the senses, the distorted perspective is that of what can be observed with the five senses.
“Sensation, which by its very nature is dependent on the object and objective stimuli, undergoes considerable modification in the introverted attitude. It, too, has a subjective factor, for besides the sensed object there is a sensing subject who adds his subjective disposition to the objective stimulus. In the introverted attitude sensation is based predominantly on the subjective component of perception. What I mean by this is best illustrated by works of art which reproduces external objects. If for instance, several painters were to paint the same landscape, each trying to reproduce it faithfully, each painting will be different from the others, not merely because of differences in ability, but chiefly because of different ways of seeing; indeed, in some of the paintings there will be a distinct psychic difference in mood and treatment of color and form.” Psychological Types PPs 393-394.
However, the mind of the Introverted Sensing type does not distort the abstract vision of how the world tends to work. That is the case because the function responsible for creating the vision of how the world tends to function is Intuition. The Intuition of the Introverted Sensing type is Extroverted. Therefore there is no such distortion.
Another important note: Our attitude towards functions that we are not comfortable with is negative. That is simply because we experience negative emotion when engaging in such functions. In the case of the Introverted Perceiving type, the negativity is directed towards extroversion. As this is the faculty that the Introvert is uncomfortable with. Hence, the Introverted Sensing type tends to have a negative attitude towards the external environment which can be observed with the senses. We also know, as we have established before, that the Introverted Sensing type tends to take the aforementioned external environment very seriously. Hence, he tends to feel a very strong urge to ensure that the external environment that can be observed with the senses is exactly the way he feels it should be.
What can we conclude about the Introverted Sensing type at this point?
The Introverted Sensing type is very sensitive to the external, physical environment as it is fundamental to his inner being. The obsessive compulsive disorder is an exaggeration of a malfunction Introverted Sensing type. Or in other words, an exaggeration of a personality of an individual who over-relies on the Introverted Sensing faculty. It should also be noted that because Sensing is a dominant faculty of the Introverted Sensing type, and sensing only interacts with what is available at the present moment, this type tends to be focused strictly on the current moment. For this reason, the type can easily be intensely focused on what is currently taking place in his life. Such a focus can be so intense that what may be, or what likely will be shall be ignored. This is also the case because Intuition is the inferior faculty of the Introverted Sensing type. One needs to use Intuition in order to imagine the possibilities of what may happen in the future, or imagine any kind of a scenario that is not the current scenario. As we have established earlier, we tend to have a negative attitude towards faculties that are antithetical to our natural dispositions.
The dispositions of the Introverted Sensing type are antithetical to that of Intuition as Sensation by definition is antithetical to Intuition. Hence, the ISTJ tends to have a strong tendency to be focused intensely on the present moment and paying almost no attention to the external world. Because Intuition is an inferior faculty, the ISTJ tends to be averse to speculation, or long-term planning with regard to his current situation. This leads him to adapt the ' we will see how to go about this situation, when we get there' mindset.
The Introverted Sensing type also struggles to improvise more than any type. This is because he lacks the fluidity of the Extroverted Perceiving type. That is the case because Extroverted Perception interacts with the environment directly. For this reason the EP types are observed effortlessly and quickly interacting with the external environment. EPs tend not to be planners. Introverted Perceivers tend to filter their external environment through their unconscious psyche. And as we have established earlier, the perceptions of the external environment of the Introverted Perceiver tend to be distorted. Because they tend to be distorted, it is close to impossible for the Introverted perceiver to adequately interact with the external world.
The salient different between the Introverted Sensing type and the Introverted Intuitive type is as follows. The Introverted Intuitive type is highly imaginative as aforementioned. For this reason, he is able to envisage many different ways in which he could interact with the external environment. The Introverted Sensing type lacks such an imagination. He is merely tied down to the impulses delivered to him by his sensorial perceptions. Thus, for this reason the Introverted Sensing type is tied down to only one way of interacting with the external environment. Scrupulous adherence to a routine is nearly an inevitable result of such a mindset.
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Answer to your question. This man is an ISTJ.
Why?
He is either an INTJ or an ISTJ according to the premises of the problem you have provided.
1)The claim that he is an INTJ is manifestly untenable. I see no evidence of this man's natural tendency to be intensely focused on his imagination, or abstract ideas. I see no evidence of his ability to improvise, such an ability should doubtlessly be granted by one's ability to exercise imagination. Intuition or imagination is analogous to the INTJ as logical reasoning or Thinking to the INTP. Inevitably, an INTJ would show his strong tendency towards imagination in a relationship of a 9 year duration. It is impossible for the INTJ not to show such a tendency as the definition of an INTJ temperament presupposes for the strongest of all tendencies to be imagination or intuition. Since the claim that this man is an INTJ is untenable, the conditions of our problem presuppose that this man is an ISTJ.
2)He has however shown a very strong affinity with the Sensing facutly, which is doubtlessly his strongest tendency. Carefully working out his plans with regard to even the most frivolous activities. Such as playing a computer game. Introverted Sensation is in tune with the concrete environment. Both types, due to a lack of extroverted perception, tend to be planners as improvising is unnatural to them. However, the perceptions of the Introverted Sensor lead the person in question to interact with the physical environment. Hence, he is more likely to write down his plans carefully. His perceptions of the external environment are directly tied to the concrete, physical world. Such perceptions remain in the world of imagination for the Introverted Intuitive type. The Introverted Intuitive type lacks attunement with the sensing faculty, therefore the Introverted Intuitive type has trouble interacting with the physical environment. It is unlikely for the Introverted Intuitive type to have a distinct tendency to write as neatly as possible and to carefully organize his physical environment. Moreover, his tendency to operate in the same fashion without an ambition to experience new ways of operating is also manifest.
"Food. If we went out to a restaurant, he would get the same one or two things, always. If he had a bad experience at a restaurant, even if his prior experiences were pleasant, he would never want to eat there again. "
Even though an INTJ also tends to be a creature of habit due to a lack of Extroverted perception, the sheer affinity with imagination would exhort the INTJ in question to attempt to function in novel ways sooner or later.
3) The man in question appears to lack an ambition to brainstorm. This is anathema to a temperament with a dominant Intuitive function. The man in question is intensely focused on the present moment. "He'd always say, "we'll talk about that when the time comes". "