Objection 1. It would seem that life is not adequately divided into active and contemplative. For the Philosopher says (Ethic. i, 5) that there are three most prominent kinds of life, the life of "pleasure," the "civil" which would seem to be the same as the active, and the "contemplative" life. Therefore the division of life into active and contemplative would seem to be inadequate.
Objection 2. Further, Augustine (De Civ. Dei xix, 1,2,3,19) mentions three kinds of life, namely the life of "leisure" which pertains to the contemplative, the "busy" life which pertains to the active, and a third "composed of both." Therefore it would seem that life is inadequately divided into active and contemplative.
Objection 3. Further, man's life is diversified according to the divers actions in which men are occupied. Now there are more than two occupations of human actions. Therefore it would seem that life should be divided into more kinds than the active and the contemplative.
On the contrary, These two lives are signified by the two wives of Jacob; the active by Lia, and the contemplative by Rachel: and by the two hostesses of our Lord; the contemplative life by Mary, and the active life by Martha, as Gregory declares (Moral. vi, 37 [Hom. xiv in Ezech.]). Now this signification would not be fitting if there were more than two lives. Therefore life is adequately divided into active and contemplative.
I answer that, As stated above (1, ad 2), this division applies to the human life as derived from the intellect. Now the intellect is divided into active and contemplative, since the end of intellective knowledge is either the knowledge itself of truth, which pertains to the contemplative intellect, or some external action, which pertains to the practical or active intellect. Therefore life too is adequately divided into active and contemplative.
Reply to Objection 1. The life of pleasure places its end in pleasures of the body, which are common to us and dumb animals; wherefore as the Philosopher says (Ethic. Ethic. i, 5), it is the life "of a beast." Hence it is not included in this division of the life of a man into active and contemplative.
Reply to Objection 2. A mean is a combination of extremes, wherefore it is virtually contained in them, as tepid in hot and cold, and pale in white and black. On like manner active and contemplative comprise that which is composed of both. Nevertheless as in every mixture one of the simples predominates, so too in the mean state of life sometimes the contemplative, sometimes the active element, abounds.
Reply to Objection 3. All the occupations of human actions, if directed to the requirements of the present life in accord with right reason, belong to the active life which provides for the necessities of the present life by means of well-ordered activity. If, on the other hand, they minister to any concupiscence whatever, they belong to the life of pleasure, which is not comprised under the active life. Those human occupations that are directed to the consideration of truth belong to the contemplative life.
Source: Summa Theologica (New Advent)