Objection 1. It would seem that counsel is not only of things that we do. For counsel implies some kind of conference. But it is possible for many to confer about things that are not subject to movement, and are not the result of our actions, such as the nature of various things. Therefore counsel is not only of things that we do.
Objection 2. Further, men sometimes seek counsel about things that are laid down by law; hence we speak of counsel at law. And yet those who seek counsel thus, have nothing to do in making the laws. Therefore counsel is not only of things that we do.
Objection 3. Further, some are said to take consultation about future events; which, however, are not in our power. Therefore counsel is not only of things that we do.
Objection 4. Further, if counsel were only of things that we do, no would take counsel about what another does. But this is clearly untrue. Therefore counsel is not only of things that we do.
On the contrary, Gregory of Nyssa [Nemesius, De Nat. Hom. xxxiv.] says: "We take counsel of things that are within our competency and that we are able to do."
I answer that, Counsel properly implies a conference held between several; the very word [consilium] denotes this, for it means a sitting together [considium], from the fact that many sit together in order to confer with one another. Now we must take note that in contingent particular cases, in order that anything be known for certain, it is necessary to take several conditions or circumstances into consideration, which it is not easy for one to consider, but are considered by several with greater certainty, since what one takes note of, escapes the notice of another; whereas in necessary and universal things, our view is brought to bear on matters much more absolute and simple, so that one man by himself may be sufficient to consider these things. Wherefore the inquiry of counsel is concerned, properly speaking, with contingent singulars. Now the knowledge of the truth in such matters does not rank so high as to be desirable of itself, as is the knowledge of things universal and necessary; but it is desired as being useful towards action, because actions bear on things singular and contingent. Consequently, properly speaking, counsel is about things done by us.
Reply to Objection 1. Counsel implies conference, not of any kind, but about what is to be done, for the reason given above.
Reply to Objection 2. Although that which is laid down by the law is not due to the action of him who seeks counsel, nevertheless it directs him in his action: since the mandate of the law is one reason for doing something.
Reply to Objection 3. Counsel is not only about what is done, but also about whatever has relation to what is done. And for this reason we speak of consulting about future events, in so far as man is induced to do or omit something, through the knowledge of future events.
Reply to Objection 4. We seek counsel about the actions of others, in so far as they are, in some way, one with us; either by union of affection--thus a man is solicitous about what concerns his friend, as though it concerned himself; or after the manner of an instrument, for the principal agent and the instrument are, in a way, one cause, since one acts through the other; thus the master takes counsel about what he would do through his servant.
Source: Summa Theologica (New Advent)