On Alberti's "sign": vision and composition in quattrocento painting - Leon Battista Alberti's commentary 'On Painting'

For Aquinas, however, it is the attraction of images as likenesses of something else that justifies image worship. He describes this attraction as "one and the same" as the attraction of that other thing. If this other thing were a material object, this formulation would contradict the example of the statue, in which the intellect apprehends the thing of which the statue is a likeness. But reference to Aristotle's On Memory (450b20-451a1) shows that there is no contradiction. There Aristotle compares remembrance with contemplating the likeness of a sitter in a portrait. Remembrance occurs when the soul recalls a phantasm produced by a previous perception or thought. Like a portrait, this phantasm is both a thing in itself and an icon of something else. When understood as an icon, it is a likeness of something previously perceived or thought, which derives from a prior cognition of that thing. So, too, when a portrait is contemplated as an icon of a sitter, it is a likeness of a prior cognition (for example, of what the artist saw and thought when painting), even if a viewer has not previously seen the sitter in person.(56) In a commentary, Aquinas seizes on Aristotle's discussion to argue that likenesses in paintings, even those of particular men, are objects of intellect. Like things remembered, sitters in portraits are present to viewers only as phantasms. These phantasms are cognitive likenesses, not objects of outer sense. Accordingly, "when the soul devotes itself to a phantasm insofar as it is phantasm of something else, it considers that thing as an image which we sensed and understood previously, just as is said about the painting. . . . [In both cases, the movement of the soul] is like an act of phantasia or imagination or even of intellect, when considering a universal thing."(57) Thus, like universals and prior cognitions, the likenesses of things represented in images are intelligible to the soul by apprehension.

I propose to call the apprehension of images as likenesses the 'signification function.' According to a famous definition by Saint Augustine, which is quoted by Thomas Aquinas and many other medieval and Renaissance thinkers, a sign is "a thing [or property] proper to appearance [praeter speciem] that causes the senses to fashion something other than itself in cognition."(58) Aquinas's discussion conforms perfectly with this definition. His image is a "certain thing" whose appearance causes the viewer to recognize the likeness of "something other than itself." Even if the prototype is a real thing, it is understood by apprehension, not composition and division, because it is recognized as an appearance of what the thing is rather than as a material object. This appearance makes the crafted image a sign.

Aquinas's defense of image worship accords with the devotional practice urged by the "Nec Deus" distich. For Aquinas, understanding holy images requires both judgment and apprehension, but it is apprehension that justifies image worship. The distich is a complex utterance instructing worshipers to divide and compose in order to apprehend. The first line urges division by denying that the present image is God; the second line urges composition by affirming that the sacred image signifies God. Through composition and division, worshipers fashion a phantasm of the present image. This phantasm consists of signs for the identity of the image as both a crafted material object and a likeness of God. The signs for God in the image cause sense to fashion a likeness of God in cognition. Judgment composes this cognitive likeness on the basis of what the intellect apprehends to be God in the image. In this way, devotional vision disciplines worshipers to perceive God in the image.