Aertsen coins the term “hodology” to describe what the medieval philosophers did not in their unique way of expounding various of their gothic ontologies. We could consider two contrasting approaches. In his search for a criterion of certitude, Descartes adopts a particular epistemic stance, that of universal doubt, so as to reveal by contrast the desired criterion. In order to uncover the a priori and synthetic categories of pure reason, Kant proposes a method that analyzes the givens of experience in light of his fundamental Copernican shift and his array of possible judgments. Both, although in distinct ways, begin from the experiences of the subject (the “I”) so as to terminate in a fundamental regulative principle of that subject, the central and yet hidden basis for the immediately known phenomenal life and its necessary structure. (It was Husserl’s project to ground this phenomenological approach upon a better noetic basis, avoiding rationalism and idealism.)
In contrast to these is the method implicit in Plato’s exposition of the Divided Line and the Cave. Akin to Descartes and Kant, the life of the mind begins (in the sensible part of the Line, or inside the Cave) with what is immediately available to it. Like Descartes and Kant, this immediacy tracks a given world that surrounds the “I” as its opposite; it is in a certain measure alien to it and epistemically inimical, since the shadows known by the senses fall short of the eternal verities desired by nous. However, Plato locates the foundation of the necessary structure underlying the experience of the sensible realm outside the subject (in the intelligible portion of the Line; outside the Cave). The first mode of intellectual knowledge is via hypothesis (Socrates compares it to geometry); the higher mode of intellectual knowledge is through nous alone, eschewing all hypotheses. However, lacking the ability to contemplate reality from this lofty point of view, Socrates and his companions can only proceed to discuss reality as it would be seen from the highest part of the line using hypotheses akin to those found in the first mode.
This attention to principles that are first to us and first “in themselves” or in a purported ontological order prior to the knowing subject qua object, is a distinction that Aristotle learned well from his teacher. It survives also in the Neoplatonism and gothic metaphysics of creation and angelology. The premier expositor of this method, St. Thomas Aquinas, arranges this distinction in terms of a via resolutionis and a via compositionis—a “way of resolution” or analysis, and a “way of composition” or synthesis.
Rational consideration ends in intellectual consideration according to the way of resolution, insofar as reason gathers one simple truth from many. Again, intellectual consideration is the beginning of rational consideration according to the way of composition or invention, insofar as the intellect comprehends a multitude in one. Therefore, that consideration which is the terminus of all human reasoning is most of all intellectual consideration. (SBdT, q. 6, a. 1, c. 3)
This distinction follows an image that Thomas borrows from Boethius: reasoning compares to ‘intellecting’ as time is to eternity or a circle to its center. Thus, on the one hand, reason is an illative faculty; it must proceed to a unified truth by recourse to many instances, concepts, statements, and arguments drawn from many observed effects or experiences. On the other hand, intellect is an intuitive faculty; it begins from a truth grasped in its simplicity and grounds further rational discourse. “Indeed, the intellect is able to understand many things in the mode of one thing, but not many things in the mode of the many.” (ST, Ia, q. 85, a. 4) Rather, understanding many things as many—and through many thoughts—is the work of reason. Reasoning thus begins and ends with an intellected simple. Yet the beginning and the ending cannot be intellected in the same respect: “The circularity [of reason] is observed in this, that reason arrives at conclusions from principles according to the way of discovery, and examines discovered conclusions according to the way of judgment, resolving them back into principles.” (QDV q. 10, a. 8, ad 10; Sweeney translation) One commentator observes the following about this distinction and its Boethian image:
The metaphor is apt because, like the circular path of the heavenly bodies imitating the first mover, the “circular” path of reasoning is for Aquinas the human imitation of the intellectus of God and the angels, who comprehend immediately and intuitively a multiplicity in unity and a unity in multiplicity. Ultimately and in all senses the need for resolution and composition, the movements describing and circumscribing the dialectical structure of our reasoning, is a mark of the imperfection of our imitation of the divine intellectus, of human reason as sequential rather than synoptic, as discursive rather than intuitive, in short, as incomplete yet directed from and toward principles. (Sweeney, “Three Notions,” 243.)
This circulatio rationis, or circulation within reason, furthermore, occurs in two modes: either in reality (secundum rem) or in notion (secundum rationem). The former finds the mind, in its reasoning and intellection, tracing its thinking from thing to thing; if this is by way of resolution, then this proceeds from effects to causes or from the dependent to its grounds. The latter is where the mind traces the contours of the inner forms or definitions of things; if this is by way of resolution, then this proceeds from the specific accounts and properties of things to the most general notions of being (viz., being itself, categoriality, essence and existence, modality, etc.). By contrast, the synthetic way, the way of compositions, in reality and in notion is from general causes or grounds to particular effects and dependent states of affair, or from the most common metaphysical notions of reality to the specific.