Analyst John Bebe in an article he wrote in 2006 (I can send you it if you're interested) developed the function theory to an eight-function model, in which the dominant function would be the hero archetype, the auxiliary function being the parent archetype, the puer aeternus being the tertiary function, and the shadow being the inferior function. So, if this is the case, Introverted sensation would be the puer aeternus, which would make sense, as Si (from my experience) develops in INTPs as a sort of nostalgic longing, a want for things to be simple and as they were 'before', or a longing for some other world. Characteristic of the puer aeternus archetype being the 'divine/eternal child' insofar as they want to maintain a since of innocence or naivety about life. Would you say you relate to the following description of Introverted Sensation?
"Tertiary Function: Introverted Sensing
The Sensing function is the mode of perceiving which gathers information from facts, details and objects. When this function is strongly introverted, Si, the focus moves away from external details and is primarly concerned with personal, introspective detail. The experience of the present is not central in itself, as with Se. Rather the focus is on how the present evokes remembered earlier experiences. The key outworking of the Si function is then a concern with memories of the past. INTPs typically have an acute awareness of the passage of past times. Sequences of past events can assume a remarkable solidity in their thinking, while most INTPs have very good memories. Indeed, the sensing function is usually very well developed in its strongly Si mode and forms a strong partnership with the Ti core. Hence, the internal world of the INTP is a world of complex, detailed structure, well organized and methodically kept in order. When an INTP focusses on specific details then he has a very sharp eye for them and will not lose sight of them.
On the other hand, one of the more serious weaknesses of an INTP is that the sensing function makes little inroads out into the external world. INTPs are usually oblivious to external details unless something forces them to take notice. When an INTP goes into a new room, or walks through a city street, he is blind to much of the detail that people with an Se function would see immediately. The INTP always tries to get a feel for the big picture, using his Ne, and habitually ignores all detail. Of course, objects of interest will be seen as a matter of course and he can choose to concentrate and focus on them, but it is remarkable how much he still overlooks. And those objects he does happen to notice will belong to a small set of things that he is interested in anyway. Many other objects would only be noticed if another person points them out to him.
When an INTP lives alone, his home is usually spartan and utility-oriented. There will be little or no decorative objects, electronic equipement will be in abundance and the importance of any object will depend only on its usefulness. The general style of the home is largely irrelevant. When an object is put aside, not to be returned to for a while, it will lie fully ignored until used again. Objects which lie unmoved for more than about 48 hours usually become invisible to the INTP, until such time as he has a use for them again. For other temperaments whose need for tidiness and order in a house is strong, this lack of concern in this area may seem despairing. For the INTP, however, no problem exists. Corners of rooms, table tops and cupboards may become cluttered with objects, but while they don’t move they remain effectively invisible and are unimportant. Indeed, less mature INTPs have a reluctance to move objects at all, for the desire to remain detached and not physically interact with the world can be strong. The one thing that will force an INTP to tidy his home radically, even when alone, is when the clutter eventually gets in his way and hinders some activity. Often, however, the offending objects will merely be moved into another corner where they can spend some more weeks being invisible. When an INTP lives with a partner and perhaps has a family, he learns the necessity of focussing on the details of tidiness. This is not usually difficult, since tidying a house is an activity which can be clearly defined and, hence, the INTP can focus on it by treating it as systematic work.
Introverted Sensing often plays an important role in the private world of the INTP. When he visits a place, whether new or already known, his Si function gives an overriding concern for the atmosphere or mood of the place. In his subconscious, he connects the present experiences of his surroundings with memories of his past, sometimes deep past. A sense of history, of universality, is almost always invoked. When on holiday, the INTP wants to experience above all the ambience of each location. Specific details in the present are relatively unimportant and will not be well remembered. However, the atmosphere or mood will be remembered long after, as though it were a solid object. Since people encountered on a holiday usually count as details, unless more personal contact develops, the INTP tends to be drawn more to lonely, isolated places where atmosphere is less disturbed. Nevertheless, the presence of people does add its own ambience which can also be appreciated considerably. The net result of this concern for past experiences and of mood/atmosphere is that INTPs belong centrally to those types referred to as melancolic. The INTP melancolic is typically drawn to wild polar expanses, to mountain ranges and all places on the edges of civilisation. Whatever his particular yearning might actually be, it has a common root. The homeland of the INTP’s psyche is a small and cosy community, isolated in the middle of a vast expanse of wilderness.
Because the present is inextricably linked to a sense of the past, INTPs tend to hoard items which help solidify the connection to the past. They find it very difficult to let go of anything they have collected (or indeed created) and which may have a nostalgic meaning. They assume that any object which is of interest now is bound to remain of interest for the rest of their lives. This emphasizes a strong sense of universality in the progression of time, just as it emphasizes the seriousness with which INTPs approach their interests. Frivolity is not in their vocabulary. INTPs often love keeping lists and databases in areas of interest, especially when the lists are associated with things of the past. Collecting periodical magazines or other media of interest is also a very common INTP trait. Such a collection is usually taken very seriously. Yet the collective whole, considered as a temporal rather than spatial object, always assumes more importance in the mind of the INTP than the objects forming the collection themselves. Hence, INTPs are collectors, but they are collecters for whom the objects themselves are only important in so far as they evoke a connection to past events, in so far as they yield a nostalgic mood. The curious problem with any collection of an INTP is that he typically fails to enjoy it in the here and now. Items are stored away so that they can evoke this time at some point in the future, but such a point often never occurs. It may never occur because INTPs are always so mentally active that they continually delve into new interests, and continue to hoard items relating to these, so that they rarely allow themselves enough time to reflect on the ever expanding library of their past. The interests of an INTP would be enough to occupy him for several lifetimes if that were possible.
Photography is a classic interest of the INTP, which depends strongly on the Si – Ne combination, as well as on Ti for attention to technical detail. Landscape photography, for example, is the art of conveying a sense of mood/atmosphere to the viewer (Si). The correct employment of lenses, filters etc. brings out the Ti core, while the enjoyment of seeing the world as an fascinating varied object to be observed and captured in the best possible way brings out the Ne-Ti architect. Photos are also a way of capturing the present to evoke a sense of past in the future (Si). When involved in portrait or people photography, the INTP will also be primarily concerned with the mood conveyed by the person in the eye of the lens. Quality photographic skill, as well as an intrinsic feel for imagery, is usually second nature to the INTP and can make a good career choice. When viewing photographic images, say in magazines, the overriding concern is for how the photo is conveyed; its mood, its colour, contrast and shading usages, its perspectives and image quality. However, the actual subject of the image, which other types are likely to concentrate on first, takes a back seat unless it is unavoidably dramatic. Hence, INTPs may convey a very critical and impersonal approach in discussing images, which could lead to offence in some situations.
Another area of interest common to INTPs, where Si has a strong influence, is Music. INTPs are usually fascinated by music and may have deep and wide-ranging tastes. Indeed, each of their three main functions (Ti, Ne, Si) plays a role in the enjoyment of music, and indeed music is a key interest for bringing out the feeling shadow of the INTP. Si itself brings a fascination for mood and atmosphere in music as well as for a strong sense of personal nostalgia. INTPs are therefore often keen on melancolic minor-key music in which an introspective and/or esoteric mood is conveyed. Equally, INTPs enjoy hearing music that they heard and enjoyed when younger (provided they can still appreciate it now) and yearn for the sense of nostalgia that it yields. INTPs are also drawn to complexly structured music, thanks to their Ti core. An appreciation of modern classical music, as well as perhaps contemporary jazz, is therefore common with them. Such music types are usually too complex to be understood after a single hearing, which hence provides excellent material for analysis, exciting the INTP no end. Once the basic developmental structure of the music has been assessed, Ne provides the impetus to derive a general meaning of the piece. What does the composer wish to convey, for example? Why was that particular development chosen? Indeed, the Ne is usually hard at work during listening sessions, trying to grasp the meanings behind the often fascinating combinations of sound-world evocations, structural developments
and nostalgic impressions.
When the Ti core dominates the choice of music to listen to, the need for intellectual stimulation derived from complex structures and sounds will override concerns for cultured harmony. Hence, INTPs are often drawn to dissonance. Indeed, they may even thoroughly strive for dissonant sound worlds. When in such moods, consonant harmonies, especially of the three-chord-melody variety, are dismissed as boring and uninspired. If an INTP is forced to listen to simple harmonic music for a while, he usually can’t wait to feel the relief provided by a few minutes of pure dissonance. The ideal music for the Ti core might be typically a modern symphony, with a complex, but analysable structure, with a rich and varied sound world, predominantly dissonant but with sections of melodic motifs to provide solidity. Examples of modern classical composers who particularly speak to the Ti core might be Simpson, Arnold, Holmboe, Maxwell-Davies and Shostakovich.
However, feeding the Ti core alone with music will rarely satisfy an INTP for long. Where music really inspires in when the Si function is brought into the picture. Generally, INTPs are fascinated by atmospheres evoked by music. Examples of modern classical composers whose music speaks more to the Si-melancoly through sound-world evocation might be Bax, Tavener, Pärt, Szymanowski and Rautavaara. Some elements of world-music also speak strongly to the Si-melancoly. INTPs may be interested in the Folk musics of eastern Europe and India, for example. The role played by the Si function is shared by SJ types, so that INTPs may find a common musical bond with some SJs in this area. Indeed, INTPs often feel at ease with SJs, especially their near-shadow xSFJ types. The SJ’s guardian instincts usually help the INTP to feel at ease, while the tradition-based predictability of the SJ approach to life helps the INTP to know where he stands, giving him the space he needs to relax. Although the most intense communicative friendships may develop with fellow NTs, some extraverted intuitive types may overstress the INTP by being too dominant and unpredictable, extracting too much energy from the Ti core.
Ultimately, however, music forms a vital, central role in awaking the underdeveloped Fe shadow in the life of an INTP. It is undoutedly Fe that gives the INTP the life-spark to introduce a genuine sense of joy that music is experienced with. To the INTP, the role of Fe in music appreciation remains mysterious. Music forms which may be useful for awakening the shadow are expressive forms of jazz, where extraverted Feeling is central to the music-making process, as well as some expressive Folk styles (Irish for example). Examples of modern classical composers whose music may appeal to the Fe shadow of INTPs are Messiaen, Copland, Schnittke, Bartok, Vaughan-Williams and, again, Shostakovich (Noting that Fe can be expressing a range of positive or negative feelings).The music of Shostakovich is a particular favourite because, alongside its developmental structure, it also yields an immense sense of passionate tragedy which awakes the Fe-shadow together with the Si-melancoly."
Taken from
here