I tried creating a discussion on Si in some old thread:
http://www.the16types.info/vbulletin...ngthen-your-Si
Si is
- irrational (thus perceiving reality through the unconscious)
- sensory (thus perceiving reality through unconsciously stored (sensory) impressions and emotions had before)
- introverted (thus filtering the perception through the ego (comparing with own (ego) states))
- dynamic (thus looking at changes between states (rather than states/situations as is))
This means Si is first and foremost great at:
- "just knowing" where a person (or societies) come from in life (family background, life path so far, how the social reality they grew up in influenced them, how the experiences had changed them)
- somewhat predicting the life path people (or societies) will take from now on based on the knowledge of their past and present (development from now on, life path from crib to death) (things like
"this person will become a slut later in life because she doesn't get any attention as a child" (Si with Fe))
Two examples of Si, both showing Si impressions of how the school system today lacks (natural) humanity and forms children into faceless creatures and results in pointless (inhuman) activity (the first example is Si with Te, the second is Si with Fe)
A bit more....
Si, just like Ni, gets stuck in the "paths" these functions perceive, in Ni's case, the mental development of people (societies), in Si's case the life path development of people (societies). Ne can surprisingly pull Si out of it's "tracks" in a similar way to how Se pulls Ni out of it's tracks.
Ne does this by just being unaware of Si and thus suggesting possible ways to ALTER the life path that Si gets stuck in, due to the strong awareness of this life path. Thus why Si can look "passive" and just "adapt" to a life path, whereas Ne can come in and surprise Si with "crazy" new opportunities for changing the tracks (changing life).
On a high level, Si can sense ancestry in people's faces (or cultures), I believe, so it goes beyond what is obviously visibly there, I've seen it done. This is similar to how Ni perceives how a society is influenced by the past mental/social structures. Si can use this to understand people or societies in a historical context. It's probably not even experienced that consciously, but it's there, giving more information.
Si is indirectly linked to "internal bodily sensations" in that the strong feeling of "from crib to death bed" can give a need to find comfort in keeping the body stable in that life track.
Si is indirectly linked to "aestetics" for similar reasons, since health levels and thus aestetics give a clue as to where people are in a life path. Artificials like too much make-up may thus be off-putting to a Si-ego as it hides the (natural) beauty of people and their (beautiful and unique) life path, I think. But it's just an indirect link imo, that isn't very useful for typing, since not all people will focus on this the same way.
Si is also indirectly linked to food, as food is part of life development (crib to death) etc. etc. etc
Si, like Ni mostly deals with the past, but can pull lines from the past into the future to predict it - or rather warn about it, like the 3 videos I post here show - and Si/Ni does this really well, as long as no huge changes occur.
An example of Si used to pull info from the past into the future, are the documentaries of Adam Curtis, who I believe is SEI. Watch and see how he pulls tangible lines from the past into the now and further into the future. All good examples of what Si is really about. Unlike Ni, Si is rather linear and the "dots" are connected through lifepaths (of people or societies or in Adam Curtis' case ideas/cultures/beliefs) (whereas Ni is jumping all over the place in unconnected strings of information.)
So I agree with inumbra, Si is generally quite poorly described and the descriptions too often deal with common, yet indirect, resulting traits of the function, rather than describing how the function really works.