I think Ni is probably the least understood function, which has really snowballed in regards to the total level of misinformation and ignorance out there. Hopefully with this post I will make things better, not worse.
Ni is commonly referred to as intuition of time, but I want to point out that is a outside-in "Ti" formulation of Ni. That is how Ni can be understood as part of a semantic set of relations (a "system").
Phenomenology, loosely, is the first-hand account of something--the "what its like" or "qualia" (the "qualitative experience" from the first person perspective). This would use language and form descriptions that differ dramatically from standard outside-in Ti descriptions but phenomenology is no less the basis for a Ti system. It is however a form of subjective understanding that is at the same time more and less useful than your standard "textbook" "3rd person" understanding of a thing. It is more useful in the sense that it really helps you understand whether you do or don't share the experience, but inasmuch as you don't and to the degree you differ, it is easier to understand more universal Ti notions of a thing, stripped of phenomenological description or taken to their highest possible level of universality...
I want to accomplish a phenomenological account of Ni by comparing 4 different types: Balzac, Dostoevsky, Jack, and Hamlet
Balzac leads with 4d Ni and it is conscious, whereas for Dostoevsky it is unconscious but it is nevertheless 4d. Jack and Hamlet both share 3d Ni in the creative position.
Reinin describes Ni as "the integrity of the internal situation" in various places. Which is on its face, for most, totally unhelpful and abstract and general to the point of meaninglessness. Perhaps it would then be helpful to compare it to Ne in order to provide some context and hopefully some clarity in light of their dichotomous relationship. Ne is thus "the integrity of the outer situation." People, I feel, generally understand Ne to mean "the actual state of the world, and its possibilities/potential"-- in other words its the holistic abstract picture of what really is out there, along with everything that has a real connection to what is objective and actual. In other words, a connection may not actually be realized, but the existence of the connection ensures the possibility that in some potential happening it could in principle. Things outside the realm of Ne are things that are either impossible in principle (logically impossible) or things that are impossible in virtue of what the actual picture of the world is (factually impossible), and that for them to be possible one would have to erroneously assume something untrue or inaccurate about the picture of things. Thus when people seem out of touch with reality in a Ne sense they don't just assume things that are unlikely but rather things that could not happen if you take a holistic and accurate picture of the world and make it "mesh" with whatever assumptions or declarations the person in question is making. This occurs on a highly abstract plane such that most the time people aren't comparing their Ne picture of the world to the actual Ne picture of the world consciously when they make errors of this kind. Believing something does not mean you likewise believe or approve of all the implications of your belief because you may not be aware of what they are. Thus people lacking in Ne tend to come to conclusions they themselves would not believe or try to make if they realized they were making them, but they don't. This is most common in Dreiser and Maxim, who work most comprehensively on the level of introverted rationality, which is a kind of calculus aimed at internal consistency, the downside to which they often draw conclusions on the basis of which that presume to say something about the world without actually referencing the "actual" world. Rather it was derived from limited information that was highly refined to come to a conclusion that was procedural probably very scrupulously drawn and error free, but it is essentially a case of "garbage in garbage out."
With that in mind the "outer situation" and its "integrity" is the idea that the intuition of the world as it really is is internally consistent with itself and complete as possible. In other words, we often conceptualize intuitions as large circles that ultimately have a self referential quality to them (they return to themselves, the snake eating its own tail), and that we tend to reject formulations of the world in "rational" terms that we see as having underlying intuitions that entail a contradiction when you see "the circle" in its entirety. We can say concern for "the circle" being free from contradiction or disharmony is the "integrity of the outer situation."
So that is Ne; what, then, is Ni? Every individual has an "inner state" which we tend to experience as our unique "mode of consciousness." It can be hard for some types to understand that other human beings experience different modes of consciousness. In this way both subjective and objective intuitions are linked, because failure to understand differences of subjective intuition amount to a failure to understand the actual status of the world. It is one data point that when overlooked amounts to a rather large "disharmony" of the outer picture, but it is founded on the fundamental inability or unwillingness to conceive other human beings as being radically (at the root) capable of fundamental differences in their state of mind. So when we fail to account for this difference (one that is termed "ontological" in philosophical circles--meaning the fundamental assumptions that form the basis of one's outlook--their intuitive "picture of the world" which they found all their opinions on) we skew the picture of the world-at-large and distort any judgements we derive on the basis of this failure to provide it with accurate data. This is how intuition is linked in the sense that you will never see 1d Ni paired with 4d Ne in the same individual, because the two are linked in a necessary relationship where you cannot have one without a sufficient degree of the other. Likewise a failure of one entails a precipitant failure of the other and vice versa, hence all the confusion between "is this really a failure of Ne or Ni?" type questions. This is the circular nature of intuition to perhaps the most abstract extent I can conceive of.
Ni is the "integrity of the inner situation", which does not necessarily mean a placid and balanced inner situation in the sense of Si, which would be like actual physical calmness (or more abstractly a "positive"--whatever that may be-- inner physical state). It means that the subjective inner world is consistent with itself and entails no contradictions; however, such a state could be a highly consistent state of tumult and agitation. Hamlet is the one most likely to experience these sturm un drang inner states: to conjure them as a "product" of creative Ni within himself and transmit them to others via Fe/Se. To contrast Ni with Si one must understand that while Si and Ni are linked in that a tumultuous state in one can very easily influence the other it is not necessarily the case, and that, further, "integrity in the inner state" in terms of Si does mean a consistent, non contradictory, physical state, which is most often seen as levels of physical states that are "sustainable" and either "productive" in the case of creative Si (LSE adjusting his inner state in order to achieve a task) or "healthy" (in terms of SLI which is aimed at ultimate health for its own sake, not task-oriented) or "epicurean" (in the case of SEI--maximal overall production of pleasure, not aimed at Te practical ends) or to "put on the party" (in the case of ESE--maximize Fe via adjustment of ones own physical states and to spread positive physical states to others).
Si is a little easier to understand in the sense that Si base, "introverts" view the world through the impact it has on their own inner sensations, and further view those inner sensations in terms of practicality or positive emotion. And for each, one word means the other; hence SEI finds the pursuit of introverted (self centered) physical states that serve to improve their emotions as the definition of "practicality", implictly (unconscious Te/Fi) by the way they live their life and acting out their program. Likewise SLI views the long term sustainability of their own internal physical states viewed in light of practical objective metrics to be the cause and measure of positive emotion--to them; achievement of these states is achievement of Fe, and conspicuous avoidance of direct Fe engagement yet seeming effortless ability to become the soul of the company (promote Fe states) is evidence to the efficacy of this strategy. To wrap up this digression, the Si egos either go about thinking in terms of Si as a product to be manipulated in the self and provided towards others as a superordinate goal that it is either "logical" (Te) or "ethical" (Fe) or as the fundamental goal unto themselves which is then promoted by serving up rational methods (Te, Fe) in order to maximize them for both the self and others. In essence SEI says to himself "what can I do to improve the mood such that I might feel better--I know I will give a compliment!" whereas ESE says "how can I improve someone's physical state in order that I might improve the mood--I know I will offer candy!" Each of these approaches can be directed at the self or others which leads to the paradoxical result of introverts treating themselves the way an extrovert would treat another person, and an extrovert treating themself the way an introvert would treat another person. It just means at that moment contrary to what they do most of the time they have inverted their prevailing attitude. This brings me to one final aside that personality is just a relatively consistent pattern of behavior manifest over time. So it means what defines you as an introvert or extrovert is not prescriptive in that it does not "control your destiny" rather one could conceivably simply act in an extroverted manner and if in doing so over time you spent the majority of your time in an extroverted way you would be by definition an extrovert. The underlying factor seems to be whether or not people biologically have the energy to do such a thing or whether their habits are in some way determined by a base energetic economy. That is still something of an open question.
Now, finally, perhaps we can get to Ni. Most people are not Ni egos, hence their internal situation is not something they consciously monitor and even less consciously manipulate (as is the case with Ni creative). The consequence of this is they fall into one or two habitual "states of mind"--they don't need more, nor do they know what such a thing would even be like, in principle. In the case of 1d Ni, these types display a habitual lack of control meaning they either habitually fall into the same state of mind that they cannot get out of (SLE/SEE) (without help, such as drugs, or an intuitive ego type), or they are "all over the place" without realizing it (ESE, LSE). This is common to all 1d functions, characterized by rigid habits, desire to change but inability to do so (valued 1d) or inability to recognize them in the first place and hence characterized by wild excesses or deficits resulting in unforeseen painful consequences (the seemingly "from nowhere" aspect adds a level of unpredictability hence randomness hence terror which amplifies the pain of it all).
LSE is easy to see when they go into their explosive bouts of anger (I recently saw a youtube of a SLE pretending to be an LSE dad who was on a tear in regards to some petty provocation out of all proportion to the situation acting like a dick to his son who hadn't seen in years). It is because their internal state of mind is so out of control that such reactions flow from the, at that time, internal picture of the world which concludes that "shits all wrong and I'm in "hulk mode" in order to correct it" the irony is what they see as internal consistency "hulk mode -- to correct" is actually out of step and thus counter productive to the real situation at hand (Ne), thus their lack of control is about to lead to negative consequences--damage to their relationships--precisely because they cannot see that their inner state is inappropriate and out of balance. My dad does this all the time, it basically is his most obvious Achilles heel, where he starts to misread a situation, which in of itself is not the worst problem, the problem is the inability to control his inner state in response to it and thus "hulk out" at inappropriate moments, moments that are inappropriate precisely because he acts in a way to destroy that which he values most--familial relations.
I'm gonna take a break now but I am eventually going to get to base and creative Ni. The thing is, this groundwork needs to be really understood to even get there, because I think not fully understanding 1) Si and 2) creative functions in general, is what snowballs into people's inability to really get a grip on Ni.
Ni is commonly referred to as intuition of time, but I want to point out that is a outside-in "Ti" formulation of Ni. That is how Ni can be understood as part of a semantic set of relations (a "system").
Phenomenology, loosely, is the first-hand account of something--the "what its like" or "qualia" (the "qualitative experience" from the first person perspective). This would use language and form descriptions that differ dramatically from standard outside-in Ti descriptions but phenomenology is no less the basis for a Ti system. It is however a form of subjective understanding that is at the same time more and less useful than your standard "textbook" "3rd person" understanding of a thing. It is more useful in the sense that it really helps you understand whether you do or don't share the experience, but inasmuch as you don't and to the degree you differ, it is easier to understand more universal Ti notions of a thing, stripped of phenomenological description or taken to their highest possible level of universality...
I want to accomplish a phenomenological account of Ni by comparing 4 different types: Balzac, Dostoevsky, Jack, and Hamlet
Balzac leads with 4d Ni and it is conscious, whereas for Dostoevsky it is unconscious but it is nevertheless 4d. Jack and Hamlet both share 3d Ni in the creative position.
Reinin describes Ni as "the integrity of the internal situation" in various places. Which is on its face, for most, totally unhelpful and abstract and general to the point of meaninglessness. Perhaps it would then be helpful to compare it to Ne in order to provide some context and hopefully some clarity in light of their dichotomous relationship. Ne is thus "the integrity of the outer situation." People, I feel, generally understand Ne to mean "the actual state of the world, and its possibilities/potential"-- in other words its the holistic abstract picture of what really is out there, along with everything that has a real connection to what is objective and actual. In other words, a connection may not actually be realized, but the existence of the connection ensures the possibility that in some potential happening it could in principle. Things outside the realm of Ne are things that are either impossible in principle (logically impossible) or things that are impossible in virtue of what the actual picture of the world is (factually impossible), and that for them to be possible one would have to erroneously assume something untrue or inaccurate about the picture of things. Thus when people seem out of touch with reality in a Ne sense they don't just assume things that are unlikely but rather things that could not happen if you take a holistic and accurate picture of the world and make it "mesh" with whatever assumptions or declarations the person in question is making. This occurs on a highly abstract plane such that most the time people aren't comparing their Ne picture of the world to the actual Ne picture of the world consciously when they make errors of this kind. Believing something does not mean you likewise believe or approve of all the implications of your belief because you may not be aware of what they are. Thus people lacking in Ne tend to come to conclusions they themselves would not believe or try to make if they realized they were making them, but they don't. This is most common in Dreiser and Maxim, who work most comprehensively on the level of introverted rationality, which is a kind of calculus aimed at internal consistency, the downside to which they often draw conclusions on the basis of which that presume to say something about the world without actually referencing the "actual" world. Rather it was derived from limited information that was highly refined to come to a conclusion that was procedural probably very scrupulously drawn and error free, but it is essentially a case of "garbage in garbage out."
With that in mind the "outer situation" and its "integrity" is the idea that the intuition of the world as it really is is internally consistent with itself and complete as possible. In other words, we often conceptualize intuitions as large circles that ultimately have a self referential quality to them (they return to themselves, the snake eating its own tail), and that we tend to reject formulations of the world in "rational" terms that we see as having underlying intuitions that entail a contradiction when you see "the circle" in its entirety. We can say concern for "the circle" being free from contradiction or disharmony is the "integrity of the outer situation."
So that is Ne; what, then, is Ni? Every individual has an "inner state" which we tend to experience as our unique "mode of consciousness." It can be hard for some types to understand that other human beings experience different modes of consciousness. In this way both subjective and objective intuitions are linked, because failure to understand differences of subjective intuition amount to a failure to understand the actual status of the world. It is one data point that when overlooked amounts to a rather large "disharmony" of the outer picture, but it is founded on the fundamental inability or unwillingness to conceive other human beings as being radically (at the root) capable of fundamental differences in their state of mind. So when we fail to account for this difference (one that is termed "ontological" in philosophical circles--meaning the fundamental assumptions that form the basis of one's outlook--their intuitive "picture of the world" which they found all their opinions on) we skew the picture of the world-at-large and distort any judgements we derive on the basis of this failure to provide it with accurate data. This is how intuition is linked in the sense that you will never see 1d Ni paired with 4d Ne in the same individual, because the two are linked in a necessary relationship where you cannot have one without a sufficient degree of the other. Likewise a failure of one entails a precipitant failure of the other and vice versa, hence all the confusion between "is this really a failure of Ne or Ni?" type questions. This is the circular nature of intuition to perhaps the most abstract extent I can conceive of.
Ni is the "integrity of the inner situation", which does not necessarily mean a placid and balanced inner situation in the sense of Si, which would be like actual physical calmness (or more abstractly a "positive"--whatever that may be-- inner physical state). It means that the subjective inner world is consistent with itself and entails no contradictions; however, such a state could be a highly consistent state of tumult and agitation. Hamlet is the one most likely to experience these sturm un drang inner states: to conjure them as a "product" of creative Ni within himself and transmit them to others via Fe/Se. To contrast Ni with Si one must understand that while Si and Ni are linked in that a tumultuous state in one can very easily influence the other it is not necessarily the case, and that, further, "integrity in the inner state" in terms of Si does mean a consistent, non contradictory, physical state, which is most often seen as levels of physical states that are "sustainable" and either "productive" in the case of creative Si (LSE adjusting his inner state in order to achieve a task) or "healthy" (in terms of SLI which is aimed at ultimate health for its own sake, not task-oriented) or "epicurean" (in the case of SEI--maximal overall production of pleasure, not aimed at Te practical ends) or to "put on the party" (in the case of ESE--maximize Fe via adjustment of ones own physical states and to spread positive physical states to others).
Si is a little easier to understand in the sense that Si base, "introverts" view the world through the impact it has on their own inner sensations, and further view those inner sensations in terms of practicality or positive emotion. And for each, one word means the other; hence SEI finds the pursuit of introverted (self centered) physical states that serve to improve their emotions as the definition of "practicality", implictly (unconscious Te/Fi) by the way they live their life and acting out their program. Likewise SLI views the long term sustainability of their own internal physical states viewed in light of practical objective metrics to be the cause and measure of positive emotion--to them; achievement of these states is achievement of Fe, and conspicuous avoidance of direct Fe engagement yet seeming effortless ability to become the soul of the company (promote Fe states) is evidence to the efficacy of this strategy. To wrap up this digression, the Si egos either go about thinking in terms of Si as a product to be manipulated in the self and provided towards others as a superordinate goal that it is either "logical" (Te) or "ethical" (Fe) or as the fundamental goal unto themselves which is then promoted by serving up rational methods (Te, Fe) in order to maximize them for both the self and others. In essence SEI says to himself "what can I do to improve the mood such that I might feel better--I know I will give a compliment!" whereas ESE says "how can I improve someone's physical state in order that I might improve the mood--I know I will offer candy!" Each of these approaches can be directed at the self or others which leads to the paradoxical result of introverts treating themselves the way an extrovert would treat another person, and an extrovert treating themself the way an introvert would treat another person. It just means at that moment contrary to what they do most of the time they have inverted their prevailing attitude. This brings me to one final aside that personality is just a relatively consistent pattern of behavior manifest over time. So it means what defines you as an introvert or extrovert is not prescriptive in that it does not "control your destiny" rather one could conceivably simply act in an extroverted manner and if in doing so over time you spent the majority of your time in an extroverted way you would be by definition an extrovert. The underlying factor seems to be whether or not people biologically have the energy to do such a thing or whether their habits are in some way determined by a base energetic economy. That is still something of an open question.
Now, finally, perhaps we can get to Ni. Most people are not Ni egos, hence their internal situation is not something they consciously monitor and even less consciously manipulate (as is the case with Ni creative). The consequence of this is they fall into one or two habitual "states of mind"--they don't need more, nor do they know what such a thing would even be like, in principle. In the case of 1d Ni, these types display a habitual lack of control meaning they either habitually fall into the same state of mind that they cannot get out of (SLE/SEE) (without help, such as drugs, or an intuitive ego type), or they are "all over the place" without realizing it (ESE, LSE). This is common to all 1d functions, characterized by rigid habits, desire to change but inability to do so (valued 1d) or inability to recognize them in the first place and hence characterized by wild excesses or deficits resulting in unforeseen painful consequences (the seemingly "from nowhere" aspect adds a level of unpredictability hence randomness hence terror which amplifies the pain of it all).
LSE is easy to see when they go into their explosive bouts of anger (I recently saw a youtube of a SLE pretending to be an LSE dad who was on a tear in regards to some petty provocation out of all proportion to the situation acting like a dick to his son who hadn't seen in years). It is because their internal state of mind is so out of control that such reactions flow from the, at that time, internal picture of the world which concludes that "shits all wrong and I'm in "hulk mode" in order to correct it" the irony is what they see as internal consistency "hulk mode -- to correct" is actually out of step and thus counter productive to the real situation at hand (Ne), thus their lack of control is about to lead to negative consequences--damage to their relationships--precisely because they cannot see that their inner state is inappropriate and out of balance. My dad does this all the time, it basically is his most obvious Achilles heel, where he starts to misread a situation, which in of itself is not the worst problem, the problem is the inability to control his inner state in response to it and thus "hulk out" at inappropriate moments, moments that are inappropriate precisely because he acts in a way to destroy that which he values most--familial relations.
I'm gonna take a break now but I am eventually going to get to base and creative Ni. The thing is, this groundwork needs to be really understood to even get there, because I think not fully understanding 1) Si and 2) creative functions in general, is what snowballs into people's inability to really get a grip on Ni.