If turning the vantage point is difficult and reading through the skull is easy, then there is a hypothesis that can account for all our data, which we called the disembodied-eye hypothesis. Suppose that patterns traced on the skin are interpreted as if they were read by a disembodied eye that has a preferred position behind the head looking forward. It would take us too far afield to discuss the pros and cons of this hypothesis; suffice is to say, that although it has some drawbacks, this hypothesis served us well as an aid to thinking about the perception of patterns traced on the skin and has not been successfully challenged by any alternative. The main attraction of the hypothesis in the contest of the present analysis of perspective is that it gives some content to the idea of projecting one's egocenter to locations in space outside one's body. Furthermore, the fact that subjects in our experiments are able to adopt a variety of vantage points when instructed to do so suggests that the egocenter (or disembodied eye) is flexible and need not to remain in one position. We are still far from a true understanding of this fascinating problem of vantage points in art and in perception in general, but, given the sorts of evidence we now have, the notion of a movable egocenter cannot be treated any more as frivolous fancy.
Fig.10.4 The Parthenon, from northwest (447-432 BCE).
We have reached the point where the fifth purpose of perspective, mentioned in the introduction, can be summarized. I claim that, for viewers familiar with perspective, powerful effects can be achieved by creating discrepancies between the natural direction of the viewer's line of sight and the line of sight implicit in the perspective of the painting (as was the case with Mantegna's Saint James Led to Execution, Figure 9.7), or by locating the center of projection high above the viewer's eye level (as in Leonardo's Last Supper, Figure 9.9). These effects achieve the goal of divorcing the viewer's felt point of view in relation to the scene represented in the painting from the viewer's felt position in relation to the room in which he or she is standing. We cannot do more, in our present state of knowledge, than to speculate on the effect of such discrepancies, which I believe induce a feeling of spirituality, perhaps one conducive to a religious experience: a separation of the mind's eye from the bodily eye. Such effects were very much in accord with the aims of the Renaissance painters, who wished to convey a religious experience through their art. For, as Paul Oskar Kristeller points out in his discussion of paganism and Christianity in Renaissance thought,
if an age where the nonreligious concerns that had been growing for centuries attained a kind of equilibrium with religious and theological thought, or even began to surpass it in vitality and appeal, must be called pagan, the Renaissance was pagan, at least in certain places and phases. Yet since the religious convictions of Christianity were either retained or transformed, but never really challenged, it seems more appropriate to call the Renaissance a fundamentally Christian age. (1961, p. 73)
Furthermore, the divorce of the mind's eye from the bodily very much in the spirit of Renaissance Platonism. Plato's thought and Neoplatonism, which had been eclipsed during medieval times, were revived by Marsilio Ficino (see 1). Kristeller writes as follows about Ficino's theory of contemplation:
In the face of ordinary daily experiences, the mind finds itself in a state of continuous unrest and dissatisfaction, but it is capable of turning away from the body and the external world and of concentrating upon its own inner substance. (1967, p. 198)
Fig.10.5 Diagram in exaggerated proportion of horizontal curvature of Parthenon.
Now I do not mean to equate Ficino's concept of contemplation with the use of perspective to separate the mind's eye from the bodily eye. Nevertheless, I do wish to suggest that such a use of perspective is in keeping with the spiritual concerns of intellectuals in the late fifteenth and early sixteenth centuries.
The lack of contemporary analyses of this issue is per- haps puzzling at first blush. However, when we recall how little was written about perspective in general during the fifteenth and early sixteenth centuries, one's surprise wanes somewhat. Furthermore, when we look back at the ground we have covered up to this point in this book, it becomes apparent that our understanding of optics, geometry, and perception is far more advanced than it was half a millennium ago. It is not surprising, therefore, that Renaissance artists had to proceed more by intuition and rule of thumb than by analysis and deduction; whatever discoveries they made were most likely in the form of tacit knowledge, which is notoriously difficult to understand and analyze. Furthermore, this is not the only time in the history of art that subtle and complex procedures were developed to achieve perceptual and spiritual effects, for which little or no documentary evidence remains, the Parthenon (see Figure 10.4) being a prime example. Just as the Renaissance artists deviated from the geometric dictates of perspective, the Parthenon deviates from mathematical regularity in several ways. One of these is illustrated in Figure 10.5. To this very day, several theories concerning the purpose of these so-called refinements compete for the favor of scholars (Carpenter, 1970; Pollitt, 1972).