I didn't say intrinsically/only, but still, S (either attitude) is concrete, N (either attitude) is abstract, and the internal perception being made there is clearly concrete, and internal concrete perception often manifests in the form of memory (it also includes internal body senses).
But OK, you give your thoughts on Si and Ni.
Ok, I'll start with Si. It does indeed deal with things that are concrete. I regard it as a preferance for facts, principals or other information that the user regards as concrete, reliable or otherwise immutable. When an Si user is presented with information, they will grade it according to how much faith they can put in it. The more reliable it is, the more it will feature in their decision making. By contrast, uncertainty brings about caution and perhaps an urge to avoid the associated risks.
Si gets in backward looking character from the fact that certainty of outcome is only really seen in things that have already run there course. Thus the SJ will examine what has gone before to find what has already worked or failed. The future always contains some uncertainty, and so the Si user will try to find the most certain way of assuring a good future.
Similarly, the SJs reputation for being able to recall lots of factual information comes about because facts are usually easier to verify than ideas, and once certified as good the fact becomes more valuable to them. This importance makes the SJ more likely to remember the fact.
This is why I do not regard the example in the thread as Si, because it is not trying to certify the image of the inside of the tree as true. It's a flight of fancy, an idea of how things might be. It's little more than a random idea that popped into the persons head and was played with for awhile to see what happened.
I'll wait to see what you think of this before saying anything more.
