The foregoing opinion is also opposed to reason. For what is received into something is received according to the conditions of the recipient. But the intellect is of a more stable nature, and is more immovable than corporeal nature. If, therefore, corporeal matter holds the forms which it receives, not only while it actually does something through them, but also after ceasing to act through them, much more cogent reason is there for the intellect to receive the species unchangeably and lastingly, whether it receive them from things sensible, or derive them from some superior intellect. Thus, therefore, if we take memory only for the power of retaining species, we must say that it is in the intellectual part. But if in the notion of memory we include its object as something past, then the memory is not in the intellectual, but only in the sensitive part, which apprehends individual things. For past, as past, since it signifies being under a condition of fixed time, is something individual.
Reply to Objection 1: Memory, if considered as retentive of species, is not common to us and other animals. For species are not retained in the sensitive part of the soul only, but rather in the body and soul united: since the memorative power is the act of some organ. But the intellect in itself is retentive of species, without the association of any corporeal organ. Wherefore the Philosopher says (De Anima iii, 4) that "the soul is the seat of the species, not the whole soul, but the intellect."
Reply to Objection 2: The condition of past may be referred to two things---namely, to the object which is known, and to the act of knowledge. These two are found together in the sensitive part, which apprehends something from the fact of its being immuted by a present sensible: wherefore at the same time an animal remembers to have sensed before in the past, and to have sensed some past sensible thing. But as concerns the intellectual part, the past is accidental, and is not in itself a part of the object of the intellect. For the intellect understands man, as man: and to man, as man, it is accidental that he exist in the present, past, or future. But on the part of the act, the condition of past, even as such, may be understood to be in the intellect, as well as in the senses. Because our soul's act of understanding is an individual act, existing in this or that time, inasmuch as a man is said to understand now, or yesterday, or tomorrow. And this is not incompatible with the intellectual nature: for such an act of understanding, though something individual, is yet an immaterial act, as we have said above of the intellect (Q[76], A[1]); and therefore, as the intellect understands itself, though it be itself an individual intellect, so also it understands its act of understanding, which is an individual act, in the past, present, or future. In this way, then, the notion of memory, in as far as it regards past events, is preserved in the intellect, forasmuch as it understands that it previously understood: but not in the sense that it understands the past as something "here" and "now."
Reply to Objection 3: The intelligible species is sometimes in the intellect only in potentiality, and then the intellect is said to be in potentiality. Sometimes the intelligible species is in the intellect as regards the ultimate completion of the act, and then it understands in act. And sometimes the intelligible species is in a middle state, between potentiality and act: and then we have habitual knowledge. In this way the intellect retains the species, even when it does not understand in act.
Whether the intellectual memory is a power distinct from the intellect?
Objection 1: It would seem that the intellectual memory is distinct from the intellect. For Augustine (De Trin. x, 11) assigns to the soul memory, understanding, and will. But it is clear that the memory is a distinct power from the will. Therefore it is also distinct from the intellect.
Objection 2: Further, the reason of distinction among the powers in the sensitive part is the same as in the intellectual part. But memory in the sensitive part is distinct from sense, as we have said (Q[78], A[4]). Therefore memory in the intellectual part is distinct from the intellect.
Objection 3: Further, according to Augustine (De Trin. x, 11; xi, 7), memory, understanding, and will are equal to one another, and one flows from the other. But this could not be if memory and intellect were the same power. Therefore they are not the same power.
On the contrary, From its nature the memory is the treasury or storehouse of species. But the Philosopher (De Anima iii) attributes this to the intellect, as we have said (A[6], ad 1). Therefore the memory is not another power from the intellect.
I answer that, As has been said above (Q[77], A[3]), the powers of the soul are distinguished by the different formal aspects of their objects: since each power is defined in reference to that thing to which it is directed and which is its object. It has also been said above (Q[59], A[4]) that if any power by its nature be directed to an object according to the common ratio of the object, that power will not be differentiated according to the individual differences of that object: just as the power of sight, which regards its object under the common ratio of color, is not differentiated by differences of black and white. Now, the intellect regards its object under the common ratio of being: since the passive intellect is that "in which all are in potentiality." Wherefore the passive intellect is not differentiated by any difference of being. Nevertheless there is a distinction between the power of the active intellect and of the passive intellect: because as regards the same object, the active power which makes the object to be in act must be distinct from the passive power, which is moved by the object existing in act. Thus the active power is compared to its object as a being in act is to a being in potentiality; whereas the passive power, on the contrary, is compared to its object as being in potentiality is to a being in act. Therefore there can be no other difference of powers in the intellect, but that of passive and active. Wherefore it is clear that memory is not a distinct power from the intellect: for it belongs to the nature of a passive power to retain as well as to receive.
Reply to Objection 1: Although it is said (3 Sent. D, 1) that memory, intellect, and will are three powers, this is not in accordance with the meaning of Augustine, who says expressly (De Trin. xiv) that "if we take memory, intelligence, and will as always present in the soul, whether we actually attend to them or not, they seem to pertain to the memory only. And by intelligence I mean that by which we understand when actually thinking; and by will I mean that love or affection which unites the child and its parent." Wherefore it is clear that Augustine does not take the above three for three powers; but by memory he understands the soul's habit of retention; by intelligence, the act of the intellect; and by will, the act of the will.
Reply to Objection 2: Past and present may differentiate the sensitive powers, but not the intellectual powers, for the reason give above.
Reply to Objection 3: Intelligence arises from memory, as act from habit; and in this way it is equal to it, but not as a power to a power.
Whether the reason is distinct from the intellect?
Objection 1: It would seem that the reason is a distinct power from the intellect. For it is stated in De Spiritu et Anima that "when we wish to rise from lower things to higher, first the sense comes to our aid, then imagination, then reason, then the intellect." Therefore the reason is distinct from the intellect, as imagination is from sense.
Objection 2: Further, Boethius says (De Consol. iv, 6), that intellect is compared to reason, as eternity to time. But it does not belong to the same power to be in eternity and to be in time. Therefore reason and intellect are not the same power.
Objection 3: Further, man has intellect in common with the angels, and sense in common with the brutes. But reason, which is proper to man, whence he is called a rational animal, is a power distinct from sense. Therefore is it equally true to say that it is distinct from the intellect, which properly belongs to the angel: whence they are called intellectual.
On the contrary, Augustine says (Gen. ad lit. iii, 20) that "that in which man excels irrational animals is reason, or mind, or intelligence or whatever appropriate name we like to give it." Therefore, reason, intellect and mind are one power.
I answer that, Reason and intellect in man cannot be distinct powers. We shall understand this clearly if we consider their respective actions. For to understand is simply to apprehend intelligible truth: and to reason is to advance from one thing understood to another, so as to know an intelligible truth. And therefore angels, who according to their nature, possess perfect knowledge of intelligible truth, have no need to advance from one thing to another; but apprehend the truth simply and without mental discussion, as Dionysius says (Div. Nom. vii). But man arrives at the knowledge of intelligible truth by advancing from one thing to another; and therefore he is called rational. Reasoning, therefore, is compared to understanding, as movement is to rest, or acquisition to possession; of which one belongs to the perfect, the other to the imperfect. And since movement always proceeds from something immovable, and ends in something at rest; hence it is that human reasoning, by way of inquiry and discovery, advances from certain things simply understood---namely, the first principles; and, again, by way of judgment returns by analysis to first principles, in the light of which it examines what it has found. Now it is clear that rest and movement are not to be referred to different powers, but to one and the same, even in natural things: since by the same nature a thing is moved towards a certain place. Much more, therefore, by the same power do we understand and reason: and so it is clear that in man reason and intellect are the same power.
Reply to Objection 1: That enumeration is made according to the order of actions, not according to the distinction of powers. Moreover, that book is not of great authority.
Reply to Objection 2: The answer is clear from what we have said. For eternity is compared to time as immovable to movable. And thus Boethius compared the intellect to eternity, and reason to time.
Reply to Objection 3: Other animals are so much lower than man that they cannot attain to the knowledge of truth, which reason seeks. But man attains, although imperfectly, to the knowledge of intelligible truth, which angels know. Therefore in the angels the power of knowledge is not of a different genus fro that which is in the human reason, but is compared to it as the perfect to the imperfect.
Whether the higher and lower reason are distinct powers?
Objection 1: It would seem that the higher and lower reason are distinct powers. For Augustine says (De Trin. xii, 4,7), that the image of the Trinity is in the higher part of the reason, and not in the lower. But the parts of the soul are its powers. Therefore the higher and lower reason are two powers.
Objection 2: Further, nothing flows from itself. Now, the lower reason flows from the higher, and is ruled and directed by it. Therefore the higher reason is another power from the lower.