Objection 1. It would seem that the process of counsel is not one of analysis. For counsel is about things that we do. But the process of our actions is not one of analysis, but rather one of synthesis, viz. from the simple to the composite. Therefore counsel does not always proceed by way of analysis.
Objection 2. Further, counsel is an inquiry of the reason. But reason proceeds from things that precede to things that follow, according to the more appropriate order. Since then, the past precedes the present, and the present precedes the future, it seems that in taking counsel one should proceed from the past and present to the future: which is not an analytical process. Therefore the process of counsel is not one of analysis.
Objection 3. Further, counsel is only of such things as are possible to us, according to Ethic. iii, 3. But the question as to whether a certain thing is possible to us, depends on what we are able or unable to do, in order to gain such and such an end. Therefore the inquiry of counsel should begin from things present.
On the contrary, The Philosopher says (Ethic. iii, 3) that "he who takes counsel seems to inquire and analyze."
I answer that, In every inquiry one must begin from some principle. And if this principle precedes both in knowledge and in being, the process is not analytic, but synthetic: because to proceed from cause to effect is to proceed synthetically, since causes are more simple than effects. But if that which precedes in knowledge is later in the order of being, the process is one of analysis, as when our judgment deals with effects, which by analysis we trace to their simple causes. Now the principle in the inquiry of counsel is the end, which precedes indeed in intention, but comes afterwards into execution. Hence the inquiry of counsel must needs be one of analysis, beginning that is to say, from that which is intended in the future, and continuing until it arrives at that which is to be done at once.
Reply to Objection 1. Counsel is indeed about action. But actions take their reason from the end; and consequently the order of reasoning about actions is contrary to the order of actions.
Reply to Objection 2. Reason begins with that which is first according to reason; but not always with that which is first in point of time.
Reply to Objection 3. We should not want to know whether something to be done for an end be possible, if it were not suitable for gaining that end. Hence we must first inquire whether it be conducive to the end, before considering whether it be possible.
Source: Summa Theologica (New Advent)