I answer that, The difference between the gift of understanding and three of the others, viz. piety, fortitude, and fear, is evident, since the gift of understanding belongs to the cognitive power, while the three belong to the appetitive power.
But the difference between this gift of understanding and the remaining three, viz. wisdom, knowledge, and counsel, which also belong to the cognitive power, is not so evident. To some [*William of Auxerre, Sum. Aur. III, iii, 8], it seems that the gift of understanding differs from the gifts of knowledge and counsel, in that these two belong to practical knowledge, while the gift of understanding belongs to speculative knowledge; and that it differs from the gift of wisdom, which also belongs to speculative knowledge, in that wisdom is concerned with judgment, while understanding renders the mind apt to grasp the things that are proposed, and to penetrate into their very heart. And in this sense we have assigned the number of the gifts, above (FS, Question [68], Article [4]).
But if we consider the matter carefully, the gift of understanding is concerned not only with speculative, but also with practical matters, as stated above (Article [3]), and likewise, the gift of knowledge regards both matters, as we shall show further on (Question [9], Article [3]), and consequently, we must take their distinction in some other way. For all these four gifts are ordained to supernatural knowledge, which, in us, takes its foundation from faith. Now "faith is through hearing" (Rm. 10:17). Hence some things must be proposed to be believed by man, not as seen, but as heard, to which he assents by faith. But faith, first and principally, is about the First Truth, secondarily, about certain considerations concerning creatures, and furthermore extends to the direction of human actions, in so far as it works through charity, as appears from what has been said above (Question [4], Article [2], ad 3).
Accordingly on the part of the things proposed to faith for belief, two things are requisite on our part: first that they be penetrated or grasped by the intellect, and this belongs to the gift of understanding. Secondly, it is necessary that man should judge these things aright, that he should esteem that he ought to adhere to these things, and to withdraw from their opposites: and this judgment, with regard to Divine things belong to the gift of wisdom, but with regard to created things, belongs to the gift of knowledge, and as to its application to individual actions, belongs to the gift of counsel.