OT - Learning

I'm sorry for the OT, but i've spend two days searching the list
archives and my personal mail archive and couldn't find what i'm
looking for.

Some months ago i recall a post on this lists about learning xslt /
serching for information, in wich the author refres to a theory, or
theorm, or postulate, that basically says something like

"the difficulty in learning something is not knowing in what part of
the subject one must start learning, since one knows nothing about it"

The author of that post also mention that it's because of such a
theorem that the learning process starts by assuming some "absolute
truths" like dogmas or postulates, start from there to learn the
subject, and later get back to those dogmas to understand why they are
true.

So can someone knows what is that theory, what's is name and author,
or something related to?

Once again, sorry for the OT, and thanks for any help.