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cf., SCG1.C45; CT.BookI.C31; Metaph.Bk12.L11
In this last question, we ask whether God's act of intellect is identical to His substance. In this question, we are concerned with establishing an entitative identity between his intellect and substance (otherwise called a "material" identity). It is to be noted that we do NOT somehow assert that that which is signified by the term intellect and substance is identical in God so that they become synonymous terms, but, that there is a higher synthesis of these two formalities, formally and eminently contained in the concept of the Deity (which we already covered in numerous places above).
Thus, we say that for God to act and to be is one and the same. His substance is not somehow actualized and perfected by his understanding. So, insofar as God is, He knows.