DE MONARCHIA OF DANTE ALIGHIERI
CHAPTER III: To actualize the whole capacity of the possible intellect in speculation and action.
1. We must now determine what is the end of human society as a whole, and having determined that, we shall have accomplished more than half of our labor, according to the Philosopher in his writings to Nicomachus.  In order to discern the point in question more clearly, observe that as Nature fashions the thumb for one purpose, the whole hand for another, then the arm for a purpose differing from both, and the entire man for one differing from all, so she creates for one end the individual, for another the family, for another the village, for still another end the city, for another the kingdom, and finally for an ultimate end, by means of His art which is Nature, the Eternal God brings into being the human race in its totality. And this last is what we are in search of as the directive first principle of our investigation.
2. In beginning, then, let it be recognized that God and Nature make nothing in vain; but that whatever comes into being comes with a definite function. For, according to the intention of the creator, as creator, the ultimate end of a created being is not the being itself but its proper function.  Wherefore a proper function exists not for the sake of the being, but contrariwise. There is, then, some distinct function for which humanity as a whole is ordained, a function which neither an individual nor a household, neither a village, nor a city, nor a particular kingdom, has power to perform.  What this function is will be evident if we point out the distinctive capacity of humanity as a whole. I say, therefore, that no faculty shared by many things diverse in species is the differentiating characteristic of any one of them. For since the differentiating characteristic determines species, it would follow that one essence would be specific to many species, which is impossible. So the differentiating characteristic in man is not simple existence, for that is shared by the elements;  nor existence in combination, for that is met with in minerals;  nor existence animate, for that is found in plants;  nor existence intelligent, for that is participated in by the brutes;  but the characteristic competent to man alone, and to none other above or below him, is existence intelligent through the possible intellect.  Although other beings possess intellect, it is not intellect distinguished by potentiality, as is man's. Such beings are intelligent species in a limited sense, and their existence is no other than the uninterrupted act of understanding;  they would otherwise not be eternal. It is evident, therefore, that the differentiating characteristic of humanity is a distinctive capacity or power of intellect.
3. And since this capacity as a whole cannot be reduced to action at one time through one man, or through any one of the societies discriminated above, multiplicity is necessary in the human race in order to actualize its capacity in entirety. Likewise multiplicity is necessary in creatable things in order to exercise continually the capacity of primal matter. Were it not so, we should be granting the existence of unactualized potentiality, which is impossible. With this belief Averroes  accords in his commentary on the treatise concerning the Soul.  Further, the intellectual capacity of which I speak has reference not only to universal forms or species, but, by a sort of extension, to particular ones. Wherefore it is a common saying that the speculative intellect becomes by extension the practical, whose end is to do and to make. I speak of things to be done, which are controlled by political sagacity, and things to be made, which are controlled by art,  because they are all handmaids of speculation, that supreme end for which the Primal Good brought into being the human race.  From this now grows clear the saying in the Politics that "the vigorous in intellect naturally govern other men." 
1. Eth. 1. 7. 21: "For the principle seems to be more than half the whole." Dante almost without exception refers to Aristotle as "the Philosopher." In Conv. 3. 5. 5 he is "That glorious Philosopher to whom Nature has most completely revealed her secrets;" "The master of human reason," Conv. 4. 2. 7; "That master of philosophers," Conv. 4. 8. 5; "The master of those who know," Inf. 4. 131. For Dante's relation to Aristotle see Moore, Studies in Dante, Vol. 1. pp. 92-156. For the translations of Aristotle which be used, l. c. pp. 305-318. Throughout the De Mon, the Ethics are called "the writings to Nicomachus," a title given them because they had been addressed by the philosopher to his son of that name.
2. De Caelo 1. 4. Dante uses a singular verb with two coordinate subjects, thus, "Deus et natura facit." So infra, 1. 11. 1.
3. Conv. 3. 15. 4: "Nature would have made it in vain, because it would have been created without any end."
Par. 8. 97: "The Good which sets in revolution and contents all the realm thou art scaling makes its foresight to be virtue in these great bodies. And not only the natures are foreseen in this mind which is of itself perfect, but they together with their preservation. Wherefore whatsoever this bow discharges falls disposed to a foreseen end, just as a thing aimed right upon its mark. If this were not so, the heaven where thou journeyest would so produce its effects that they would not be an artist's works, but ruins. And this cannot be, if the intellects which move these stars are not maimed and maimed the First, in that He has not perfected them.... I see it is impossible for nature, in that which is necessary, to fail."
Cf, De Mon. 2. 7. 1; 3. 15. 1; 1. 10. 1.
4. Pol. 1. 2. 5-8.
Conv. 4. 4. 1: "The radical foundation of imperial majesty according to the truth is the necessity of human society, which is ordained to one end, that is a happy life; to which no one is capable of attaining without the aid of others, because man has many needs, which one person alone is unable to satisfy.”
5. Conv. 3. 3. 1: “Simple bodies, the elements, have a natural love for their own place; wherefore earth always falls toward the centre, and fire is drawn toward the circumference above.”
6. Conv. 3. 3. 2: “The primary composed bodies, such as minerals.” Cf. Par. 7. 124: “I see the air, and I see the fire, the earth, and the water and all their combinations come to destruction and endure but a little.”
7. Conv. 3. 3. 3: “Plants, which are the first of animate things.”
8. Conv. 3. 2. 3: “The sensitive soul is found without the rational, as in beasts and birds and fishes.”
9. For the origin of the idea see De Anima 3; Metaphys. 12; Ethics 1. 7. 12: "The work of man is an energy of soul according to reason. Man's chief good is an energy of soul according to virtue." For the mediaeval explanation, S. T. 1. 154. 4, and 1. 79. 1, 2, 10.
"Intellectus possibilis" or "passibilis," and "intellectus agens," that is, the passive, apprehending intellect, and the active intelligence, are the two intellects of man. Cf. De Mon. 1. 16. The emphasis here is on the fact that at no given time is the potentiality of man's intellect realized.
10. Dante discusses the hierarchies, Conv. 2. 5, 6, and Par. 28, 29. Cf: S.T. 1. 54-59. Conv. 2. 5. 1: "These are substances separate from matter, that is intelligences, whom the common people call angels;" 1.c. 2. 5. 3: "Their intellect is one and perpetual;" 4. 19. 2: "Human nobility, as far as the variety of its fruits is considered, excels that of the angels, although the angelic may be more divine in its unity." That is, while the angelic nature is an uninterrupted realization of the knowledge of which each order of these beings is capable, man always approximates through a variety of ways to the knowledge that is his heritage.
Par. 29. 70: "But whereas on earth through your schools it is taught that the angelic nature is such as understands and remembers and wills,... the truth is there below confused." Dante's actus or formus is typified in angelic natures, his materia or potentia in matter, while both form and matter are found in created things.
11. Averroes was an Arabian philosopher of the twelfth century, and author of the famous commentary upon Aristotle here alluded to. He is mentioned in Conv. 4. 13. 3, and placed among the great thinkers in Limbo, Inf. 4. 144.
12. "Ad libr. tertium Ed. Venet.1552, p. 164." Witte.
13. Metaphys 1. 1: "An art comes into being when, out of many conceptions of experience, one universal opinion is evolved with respect to similar cases."
14. Conv. 3. 15. 2: "In this gaze or contemplation alone is human perfection to be gained, that is, the perfection of the reason, on which, as on its most important part, all our being depends; and all our other actions, feelings, nourishment -- all exist for it alone, and it exists for itself and not for others." L. c. 4. 4. 1: "Peace should abide among them, ... which done, man lives happily, for which end he was born." L. c. 4. 17. 16: "We must know that we can have two kinds of happiness in this life, according to two different ways, one good, one best, which lead us thereto; one is the active life, and the other the contemplative." L. c. 4. 22. 5-19: "The use of the mind is double, that is, practical and speculative, and both are delightful; although that of contemplation is most so.... Its practical use is to act through us virtuously, that is, righteously by temperance, fortitude, and justice; the speculative is not to operate actively in us, but to consider the works of God and of nature; and the one and the other make up our beatitude and supreme happiness."
Purg. 27. 93, Dante dreams of Leah and Rachael, who typify the contemplative and active life; "to see satisfies her, but me to work."
Purg. 28 realizes the dream of the active life in the person of Matilda, and Purg. 30 that of the contemplative in the person of Beatrice. It is for abandoning the contemplative life, and “following false images of good," that Beatrice reproves Dante, Purg. 30. 131.
15. Pol. 1. 2. 2: "By nature too some beings command, and others obey, for the sake of mutual safety; for a being endowed with discernment and forethought is by nature the superior and governor."