Abstraction from matter is too often sullied by the idea of extraction- that there should be a lump over here we know, and a lump over there we leave aside.It is better to imagine form as essentially communicative in two directions: it commuicates itself to matter by producing an existent material thing, it communicates itself to mind by producing knowledge of that same thing. Form mediates the double total emptiness of matter on the one hand, and the human mind on the other. It communicates to them one and the same existence, but the existence is not had in the same way.
But if the existence is not had in the same way, how can we know the thing? Do we not necessarily know it differently than it is? Here we see a crucial first premise in knowledge: truth does not require that the way we know things be the same as the way they exist. This is clear even from sensation. One and the saem roundness, or number, or change can be known by many senses. One existence is known in different ways by different senses.
Just Thomism 
humblesmith said,
November 17, 2008 at 6:27 pm
You said: “It communicates to them one and the same existence, but the existence is not had in the same way.”
Is it not rather analogy of existence? Instead of one and the same existence? One and the same form exists in the thing and in the mind in an analogous way. Or am I missing it?
a thomist said,
November 17, 2008 at 10:52 pm
There is a diversity of meanings of existence, to be sure. At the present state of my thinking on analogy, I preserve the word for a multitude of meanings such that one or some of them cannot be understood, or understood fully, without knowing some first meaning. If you see this relation here with the word “existence” you would have a bona fide analogy.
a thomist said,
November 18, 2008 at 6:12 am
I wrote a longer post on analogy and its divisions. Just to be clear, the opening sentence is in no way referring to you! I was thinking about my classroom discussions of analogy. Tell me what you think.