Truth as the adequation of intellect and things speaks to two things:
1.) The absolute character of both truth and intellect. “Thing” speaks to an object without limitation. Note how the eyes are adequate to knowing only colored things, ears are adequate to knowing only things generating percussion waves. The intellect is adequate to knowing things without qualification. The most significant points about “adequation of intellect and thing” is what isn’t there. There is no adjective or phrase limiting or restricting “thing”.
2.) The connection between proportion and truth. “To be adequate” means to be neither more nor less, which speaks to a proportion between the knower and the known. One looses this when he thinks there is a pure identity between truth as adequation and truth as correspondence. Correspondence and adequation can speak to the same reality, but “to be adequate” speaks to it as neither more nor less, whereas correspondence speaks to it as symmetrical. This idea of symmetry, though it can be helpful, is more often misleading, for it suggests that truth is some reduplication of the thing in the intellect (which, as Husserl points out, would lead to an infinite regress).
The account of truth as adequation speak to truth as both absolute and proportionate. There is a certain tension between these two, which is intentional. On the one hand, truth is unlimited and extends to all things without qualification, on the other hand truth requires a proportion between intellect and things- which allows for the logical possibility that some “things” would exceed or fall short of proportion to our intellect. Intellect is at once unlimited and yet set within proportionate limits to “things”. This is not a contradiction so far as the things outside of the proportion to intellect can never be called things in the same way as things proportionate to the intellect. Aristotle discovered first how the human mind uses analogy to deal with this tension: for we call all we know “things” even though on the one hand intellect knows being without qualification or limit; but on the other hand there are “things” like matter which fall beneath a proportion to our intellect, and “things” like souls and immaterial substances that exceed proportion to our intellect.