A term that designates the immaterial mode of existence an object acquires when it is united to the intel lect in the act of understanding. It is also used to designate the mode of existence of an object in the external and internal senses. While practically all modern Thomists refer to intentional species and to impressed or expressed intelligible species, St. thomas aquinas did not use these expressions. He frequently used intention and species (and also form) interchangeably; and while he used intention as synonymous with concept, he distinguished intention from intelligible species. In view of such a diversity in usage, this article first explains the notion of intentionality in the teaching of St. Thomas and then treats of the later scholastic development of intentional species, the importance of intentional species in scholastic philosophy, and the rejection of the notion in modern philosophy.
Thomistic Notion. St. Thomas's theory of knowledge rests on a principle accepted by all scholastics, namely, that the intellect is a faculty of an immaterial and subsistent soul (see faculties of the soul). In light of this principle, the concept, or intention, whereby the intellect understands a thing must have the same mode of existence as the intellect itself; namely, it must have an immaterial existence. Furthermore, because the intellect is immaterial, the essence of a material object as understood is identically the same essence for every individual object that possesses the same specific nature. For instance, the concept man is used to designate a particular individual and every human person. Thus the concept is said to be universal (see universals). As opposed to this, the intentional species in the external senses and imagi nation, while immaterial to a certain degree, are not universal; they are merely individual intentions because the faculties involved are bodily faculties.
Intelligible Species. Thus, one must understand the analogous manner in which St. Thomas refers to a spiritual transmutation of a sensory organ, as when the eye is affected by something visible "when it receives the intention of color" (Summa theologiae 1a2ae, 22.2 ad 3). When the eye beholds gold, the gold is not in the eye, although its intention is. Thus the union of gold and the eye cannot possibly be conceived as a material union. Similarly, the imagination forms an intention of gold that enables the knower to image the gold in its absence. And just as the intention of gold must exist in the imagination in a manner different from that in which it exists in the external sense, so the intention of gold must exist in the intellect in a manner appropriate to the intellect. Therefore, the intellect must immaterialize, as it were, the sensible species found in the imagination. From the image in the imagination, the intellect must abstract an intelligible species. And it is by means of the intelligible species that the intellect forms a universal intention.
It should be noted that the concept has a nobler existence in the intellect than the image has in the imagination. Hence, the imagination can in no way be considered the efficient cause of a concept, since no agent can produce an effect nobler than itself. Reflections such as these on the causality involved in the formation of a concept led Aristotle to develop a theory of abstraction that has become traditional among scholastics. The efficient cause that alone is capable of producing the concept as its proper effect is the intellect itself; the image in the imagination is only a material cause, while the intelligible species is an instrumental cause.
Intentions. Contrary to the teaching of many scholastic textbooks, St. Thomas makes a distinction between the intelligible species and the intention, as mentioned above. For Aquinas, the intelligible species is the means whereby the intellect understands the intention, which is the terminus or term of the abstractive process: "Now since this intention as understood is the terminus of the intellectual operation, it is distinct from the intelligible species … which should be considered as the principle of the intellectual operation" (C. gent. 1.53). The intelligible species is a principle not as an efficient cause but as the first act of the intellect in the order of understanding.
Furthermore, St. Thomas divides concepts into first intentions and second intentions (In 1 sent. 23.1.3, 26.1.1 ad 3). The first intention is a concept that has an immediate foundation in reality, as the concept of man, tree, dog, etc.; whereas the second intention has only an indirect foundation in reality, such as the concept of universal, species, etc. (see logic). Thus St. Thomas's understanding of intention in the intellectual order remains distinct from that of the intelligible species. Only during the later scholastic development of his doctrine did the intelligible species come to be identified with the intentional species.
On the other hand, St. Thomas frequently uses the terms "species," "form," and "intention" to signify the same thing. This is particularly evident when he treats of the manner in which the object is represented by the various internal senses, i.e., the imagination, memory, cen tral sense, and the cogitative, or estimative, power. For instance, in arguing for a distinction between each of these powers, he states that "the power that receives the species of sensible things must be distinct from the power that preserves them" (Summa theologiae 1a, 78.4). Then, in the same context, he uses the terms "form" and "intention": "The phantasy or imagination is ordered to the retention and preservation of these forms … and the es timative power is ordered to apprehending intentions that are not received through the senses" (ibid. ).
Scholastic Development. The later scholastic philosophers simplified the manner of specifying the way in which the object is received and represented by various powers, or faculties, by adding the qualifying terms "impressed" and "expressed" to their designations of sensible species and the intelligible species. Since the external senses are passive with respect to their objects—for the change a sense undergoes is in the order of an impression only—they held that there is only an impressed sensible species in the external senses. In the internal senses, on the other hand, since the object is both received and understood, there must be both an impressed sensible species and an expressed sensible species. Likewise, in the intellect there must be an impressed intelligible species and an expressed intelligible species, the latter corresponding to the intention or concept of St. Thomas.
These usages had been fairly well established before the time of john of st. thomas, who used them in his interpretation of St. Thomas's theory of abstraction. Contemporary Thomists follow John of St. Thomas in this respect, standardizing scholastic terminology along the lines just indicated. In a still later development, the intention itself was designated as the intentional species. The expression intentional species came to be current among scholastic philosophers when it became necessary to defend the entitative character of intentions in the intellect against thinkers who reduced all knowledge to a sensory level (see M. Maher, Psychology: Empirical and Rational [New York 1930] 52).
Importance. In Thomistic epistemology it is of utmost importance to emphasize that the intentional species, or concept, as a formal sign of something in reality, does not have any signification other than the thing itself. Thus it cannot be viewed as a mere instrumental sign, having a signification of its own apart from what it represents in reality. When something is said to have an intentional mode of existence, this manner of speaking signifies that the object in reality is understood by the intellect. In this way it is maintained that the intellect does not understand the concept as such, but that the intellect understands the object in reality through an intentional being such as a concept. To maintain that the intellect understands the concept as such would be to profess, at least implicitly, conceptualism or idealism, positions that St. Thomas took pains to avoid in elucidating his theory of knowledge. A correct interpretation of the intentional species, on the other hand, enables the realism of Thomistic philosophy to be preserved.
Modern Philosophy. The intentional species is rejected by those modern philosophers who make no distinction between mind and matter, namely, proponents of materialism, sensism, naturalism, etc. It is rejected also by existential phenomenologists who adopt a purely empirical approach to reality. It is rejected too by American pragmatists, such as W. james and J. Dewey, whose theories of knowledge are confined to sensory experience. It is further rejected by those who disavow the so-called faculty theory of knowledge, as does A. N. whitehead.
Whenever intentional species are rejected, the only alternative is a nominalistic interpretation of concepts in their relation to objects: terms as arbitrary symbols derive a meaning only when they are applied to individual objects. For scholastics, the opposite is true: terms derive their meaning from objects. In symbolic logic, the term "intention" refers to the meaning that arbitrary signs acquire when viewed in relation to each other; the relation of such signs to reality is regarded as more descriptive than existential (see logic, symbolic). As a further difference from usage within the scholastic tradition, the term is spelled differently, as "intension."
See Also: intentionality; knowledge, process of; knowledge, theories of; nominalism.
Bibliography: j. e. royce, Man and His Nature (New York 1961). r. e. brennan, Thomistic Psychology (New York 1956). j. maritain, Distinguish to Unite, or The Degrees of Knowledge, tr. g. b. phelan (New York 1959); Bergsonian Philosophy and Thomism, tr. m. l. and j. g. andison (New York 1955). john of st. thomas, Cursus philosophicus thomisticus, ed. b. reiser, 3 v. (new ed. Turin 1930–37).
[r. j. masiello]