In his book, Secret Knowledge, the English painter, David Hockney, sets out a remarkable theory of the history of art, arguing that painting became much more realistic and optically exact following the invention of classical perspective in 1420 thanks to the availability of imaging devices, such as curved mirrors or ground lenses. His Great Wall above illustrates the transition.

According to Hockney’s analysis, many peculiarities of perspective, lighting, and composition found in the works of such artists as Van Eyck (±1390-1441), Caravaggio (1571-1610), Ingres (1780-1867) and others can be seen as evidence of the use of lenses, mirrors, and cameras of various kinds—and in some cases at least would have been impossible without them.

In the view of another, independent researcher, Philip Steadman, the content, composition, and sizes of most of Vermeer’s (1632-65) extant paintings indicate that he used a camera obscura to produce them (a fore-runner of the photographic camera with a screen onto which the image was projected). There is evidence that Vermeer owned lenses, and Hockney and Steadman point out that effects such as halos, large foreground objects, and out-of-focus regions can be seen in Vermeer’s paintings that would only have been evident in optically projected images (left). Many of Vermeer’s paintings certainly look like photographs to a modern eye (particularly when compared with contemporary works in the same genre), and careful measurement and analysis of their contents by Steadman strongly suggests that they were painted from scenes which often re-used the same objects and furnishings in ways consistent with the optics of a camera-obscura.

However, such theories remain controversial, and one obvious criticism is the question of why, if such optical devices were in common use by at least some artists, is there not more historical evidence of their existence? Hockney’s answer is that these were trade secrets and proprietary knowledge that artists naturally kept from one another, competing as they were for the available commissions. Nevertheless, as Hockney himself points out, his critics’ “main complaint was that for an artist to use optical aids would be ‘cheating’; that somehow I was attacking the idea of innate artistic genius.” 

Genius is a mentalistic property—indeed a quintessential one—and perhaps it is the conflict between mentalistic and mechanistic styles of thinking that explains both this complaint and why painters who may have resorted to lenses and mirrors perhaps preferred to give the impression that they had used what Hockney graphically calls “eyeballing.” Eyeballing relies critically on the personal skill of the artist and so can be represented as entirely mentalistic and uncontaminated by reliance on mechanical aids. To this extent, excellence that results from eyeballing is preferable to brilliance that comes from knowing how to handle imaging devices like a camera obscura—difficult as these are to use in practice, and peripheral as they inevitably remain to the finished work of art. In other words, artists would always prefer that their public attributed excellence to themselves personally, and so strive to keep their distance from the less mentalistic, more mechanistic world of technology and science.

But if the view of genius implied by the diametric model of cognition is correct, Hockney and Steadman have nothing for which to apologize. According to this way of looking at it, genius represents a creative and balanced extension of cognition in both the mentalistic and mechanistic directions well beyond the limits of normality. Up to now—and with the exception of detective fiction—I have tended to discuss the new insight mainly in the context of scientific genius, but Hockney and Steadman’s researches suggest that it applies to art just as well.

Their studies reveal one side of the true genius of post-Renaissance Western art by showing how it extended painting in the mechanistic direction thanks to its mastery of imaging technology, chiaroscuro, and perspective. Indeed, and with the diametric model of mental illness in mind, the contemporary comment that “The daguerreotype …  with its rectitude and slightly brutal boldness, had the effect of a sage who tells the truth bluntly” recalls parallel comments often made about high-functioning autistics!

And of course, once it had extended the technical reach of depiction in this autistic direction, Western painting could then extend itself in the opposite, mentalistic one by putting its new found mastery of realism to work in depicting a vastly greater range of expression, emotion, and feeling than was ever possible before. This, mentalistic dimension of art, has never lacked appreciation, but we have Hockney and Steadman to thank for revealing the full, fascinating extent of post-Renaissance Western art’s mechanistic genius.

At the very least, their insights suggest that, as I have pointed out before, the diametric model goes far beyond the cliché of the "Two Cultures," and reveals that the real issue is the existence of two, parallel cognitive systems, themselves coded by conflicting sets of brain-building genes.

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