Metaphysics and Ontology IV

E. What is the Role of the Senses in Acquiring Knowledge?

We have been surveying some of the metaphysical issues of the fourteenth century, issues that were still of concern when Luther was studying for his M.A. at Erfurt. We have discussed the question as to the proper subject matter of metaphysics, the relationship between the essence and existence of a thing, the issue of actuality and potency in incorporeal beings, and the question of the ontological status of universals with concomitant inquiry into the nature of individuation and identity.  Another important issue for 14th century theologians concerned itself with the metaphysics of knowing and the reliability of sense perception in acquiring knowledge.  Since the development of Christianity presupposed an Augustinian standpoint in which philosophy is in conformity with the revealed tenants of the christian faith, the task was to retain the harmony of faith and reason while still allowing empirical  access of, and affording general ontological status to, the external, non-divine world.

It is important to recall that Augustine and much of the Christian tradition presupposed the doctrine of divine illumination, holding that the mind confronts not its own concepts or ideas, but ideae, rationes, forms or species.  These were trans-subjective entities, not "subjective mental features" (Owens, "Faith, Ideas, Illumination and Experience," in The Cambridge History of Latter Medieval Philosophy, p. 442).  As Aristotle was rediscovered in the West, however, it became more important to give an account of the possibility and limits of knowledge gained through sensation, an account that sometimes produced considerable tension with the older illumination theory.  The problem was how to proceed in producing such an account, when knowledge was thought to be an incorporeal affair.  In other words,  how could the realm of the corporeal cause the suitable movements in the incorporeal assumed necessary for knowledge?  Whereas the Neoplatonic illumination starting point privileged the ontological status of ideas over material objects, (and in so doing assumed that secondary substance had more reality than primary substance), the Aristotelian focus on the ontology of primary substances seemingly reversed the situation entirely, affording no real existence to ideas -- and demoting secondary substance to a matter of the conceptual.

In the early part of the thirteenth century William of Auxerre tried to reconcile the older view of the divine illumination of religious faith with Aristotle's notion that we can attain knowledge through the senses.  He did this through developing Aristotle's assertion in De Anima that "the soul is in a way all things" (p.445).  William reasoned that although the thing known is potentially in the knower, the material intellect nonetheless had to receive its species from corporeal objects (p. 446).  The material intellect must receive the form abstracted from sensible things, forms called by his time species.   Owens writes: "the existence of things in the Augustinian intelligible world was being aligned with their potential existence in the soul's material intellect, and in each case 'existence' was regarded as metaphorical" (446).

William, however, rejected the Aristotelian notion of the active intellect, believing instead that the material intellect could itself know singulars and universals, and make true judgments about them.  (His view might be regarded as a precursor to the positions assumed by Hobbes, Locke and the other empiricists, for the object itself somehow impresses its species upon the thinker thereby forming an idea.)   Albert the Great, however, writing in 1245 advocates that an agent intellect is clearly needed in order to get the species into the material intellect.  He writes, "".  .  . unumquodque phantasma set particular determinatum: et ideo neccese est ponere agem universale in intellectu" (Summa de creatione II, 55, 1, ad 2m; Owens, p. 448).   The light of the active intellect, supplemented by the light of the uncreated intelligible light, abstracted the species from the sense particular and "lit" up the material intellect by so doing.   In combining the Aristotelian idea of abstracting the species and  forming the potential intellect with the notion of light, Albert attempted to retain Augustinian-inspired illumination theory even while moving towards an Aristotelian position on knowing the objects of the senses.   Roger Bacon, however, rejects what he sees as Albert's concession to Aristotle, holding instead that the operation of the potential and active intellect can be wholly understandable from the standpoint of Augustinian illumination theory.

As is well-known, Thomas Aquinas wholly rejected illumination theory, holding knowledge depended upon an identity in difference between the human knower and the object known.  He writes:  "Secundum autem quod intelligit res alias, intellectum in actu fit unum cum intellectu in actu, inquantum forma intellecti fit forma intellectus, inquantum est intellectus in actu, non quod sit ipsamet essential intellectus . . . quia essentia intellectus manet uno sub daubus formis secundum quod intelligit res duas successive" (Aquinas, Sent., 49, 2, 1, ad 10m; Owens, p. 452).  While Aquinas spoke of universals existing in the thing, this way of speaking was derived from the actual existence of universals only in the mind (453).

Three more thinkers deserve comment, Henry of Ghent, Duns Scotus and William Ockham.  While we mentioned all three before, we did not connect any of the three to the question of illumination and the intellect.   As we discussed earlier, Henry spoke of the intentional object having a type of existence (esse essentia) that could be distinguished from the actual existence of the thing (esse actualis existentiae).  Henry thereby explicitly connects the possession of true sense knowledge with the doctrine of divine illumination (Owens, 454).  Scotus rejected illumination theory, claiming that the divide between particulars that really exist and universals that are mere abstractions from particulars is too sharp, and accordingly there must be some common nature by virtue of which Socrates and Plato are common to men and not Socrates and a tugboat.  Some type of unity and commonness must exist outside the mind, grounding the human mind's abstraction of a common nature among objects.  This nature was thought to be formally distinct from the haeccity (or individuating nature) of a thing.  Scotus held that this nature could be known either intuitively as existing or abstractly without regard to existence.  In a tipping of the hat towards illumination, Scotus admitted that considered abstractly an object's common nature could be seen to lie before the gaze of the mind illuminated by the divine.  William of Ockham rejected the notion of illumination entirely, however, claiming that special divine intervention could cause intuitive cognition in a subject even in the absence of an object.  Accordingly, it was not the character of the object that distinguished abstract and intuitive knowledge, but the nature of the acts themselves (p. 457).

Since there was rich discussion of intuitive and abstractive cognition in the fourteenth century, it might be useful to reflect more deeply on the distinction between intuitive and abstractive cognition.   Scotus held that the fundamental distinction between abstractive and intuitive cognition is modal: the latter deals with what is possible or necessary, while the former deals with what is actual (John Boler, "Intuitive and Abstractive Cognition," in The Cambridge History of Later Medieval Philosophy, p. 465).  Ockham understands intuitive cognition to concern the apprehension by which contingent propositions are cognized, and abstractive cognition simply as a cognition that is not intuitive.  For Ockham, intuitive cognition is "caused by this one rather than that one" (Bohler, p. 468).  Yet, pace Scotus, the object need not exist for Ockham to have an intuitive knowledge of it.  The distinction between the two can be understood this way: Scotus believes that the proper place for an act of knowledge to begin is in the object, Ockham holds that it properly commences in an act of unconditional beginning.  God causing an intuitive act of cognition in the absence of an object nonetheless forms an unconditional beginning to the act. Indeed, God can cause apparent intuitive knowledge of all kinds of non-existents through His potentia dei absoluta, the absolute power of God whereby he can do anything that does not involve a contradiction.  Interestingly enough, however, appeal to potentia dei absoluta did not seem to spur development of skeptical thinking in the 14th century as did Descartes' analogous appeal to the "evil demon" two centuries later.

It is intriguing to contrast Ockham, Scotus and Thomas on knowledge of singulars.   For Ockham, knowledge occurs through the application of the concept to the individual; for Scotus, through the apprehension of unity of the individual represented by a set of characteristics; for Thomas, by means of the "construction" of the object by the intellect through the organization of sensory data (Boler, p. 476).  The intellect, according to Thomas, provides the form by which the sensory manifold is constructed.  While Aquinas' view might have some similarities with Kant, the trajectory of Scotus and Okham is definitely toward the ontology of the individual assumed at the dawn of the Enlightenment.