'There is no such thing as an empty space or an empty time. There is always something to see, something to hear. In fact, try as we may to make a silence, we cannot.' ― John Cage
Philosopher Mikael Pettersson, explores the causal status of shadows and absences in photography. Despite the apparent absurdity of the issues he raises, the implications are profound.
For a conference presentation at the Institute For Advanced Study at Durham University, Pettersson began by reference to the widely held view that photography is a prototypical causal medium wholly dependent upon the known regularities of the universe for its efficacy. If it so happened that photography were an unreliable medium, if every exposure were a struggle with uncertainty and every image were a tapestry of the indeterminate, there would be little value in these objects that so conveniently find their way into our lives. Indeed, if photography lacked causality, it seems unlikely that vision itself would be possible.
But if photography is a causal medium, Pettersson asks, how can non-entities like shadows and other kinds of absence commonly depicted in photographs have causal influence and, moreover, what is their causal foundation?
It is tempting at this stage to throw our hands in the air and to declare the preposterousness of the enquiry. Absences, and this necessarily includes the complete absence of illumination, lack causal influence because there is literally nothing to do any causing. The box of photographic paper that sits on my desk, awaiting exposure to light, gains it's value by virtue of its complete and unalterable insensitivity to the absence of light. We discern shadows in images due to the causal presence of light and its varying intensities precisely because the absence of light has no influence whatsoever. Photographic traces that depict shadows are the result of electrochemical processes designed to replace unexposed portions of the image with chemicals that absorb light, thus simulating darkness.
But to pursue this line of response to Pettersson's enquiries would be to overlook one of the most important enigmas of human, and to an indeterminate degree also creaturely, concern. Possibly the most profound event in any life is the encounter with the death of another. Absences cause—or at least seem to cause—some of the most intense experiences we are ever likely to face. So the question over the possible causal influence of absence is by no means a trivial one. It is arguably the most significant question of all.
Another conference delegate, Vivian Mizrahi, questioned Pettersson's emphasis on photography. Why, she asked, does the same not apply to other forms of image making? For Pettersson, the widely accepted causal directness of photography, the fact that it is not mediated by the brain—as is the case with drawing or painting, seems to provide stronger grounds for attributing a causal role to absence rather than any mind-dependent intermediary. Nonetheless, minds do play an inescapable role in the reception and interpretation (or 'seeing-in') of images. This was the concluding point to which Pettersson turned his attention, though not without giving due consideration to several of the more plausible but ultimately unsatisfactory acausal theories of influence in absentia.
Is there any evidence of the causal influence of absence? It might be argued that the absence of food in our stomachs causes us to seek sustenance; or that a lack of time causes lateness; or that a hole on a beach causes sand to infill the void; or that the absence of aerodynamic lift causes an airplane to fall from the sky. All of these instances, and many more that we could enumerate, are seemingly plausible examples of the causal influence of absence. However, on inspection, many turn out to be cases of commonplace causality. A decrease in blood glucose, triggers hunger; lateness is caused by an over abundance of things to be done and falling is caused by the release of potential energy.
However, the last example mentioned above is far from clear-cut. Some theorists would claim that the release of potential energy is due to an absence of physical support. There seems to be growing theoretical uncertainty over whether such instances are the result of an oversimplification in description or whether there genuinely are cases of negative causation. Personally, I'm not sure - though I suspect that the fault is linguistic in origin. If exhaustive detail were necessary to describe the causal history of even the most basic state of affairs, the chain of causes would lead inexorably to the Big Bang. Abstraction in description is therefore both necessary and inevitable. At some point even the most exhaustive account falls silent. The concept of absence then, like the concept of zero, is a tool that has proven to have enormous efficacy for us. Yet unlike the concept of zero, which is only ever acquired through education, there is evidence to suggest that human infants display an awareness of absence from a very early age and many animals also behave in ways that suggest a capacity to register absence.
However, the last example mentioned above is far from clear-cut. Some theorists would claim that the release of potential energy is due to an absence of physical support. There seems to be growing theoretical uncertainty over whether such instances are the result of an oversimplification in description or whether there genuinely are cases of negative causation. Personally, I'm not sure - though I suspect that the fault is linguistic in origin. If exhaustive detail were necessary to describe the causal history of even the most basic state of affairs, the chain of causes would lead inexorably to the Big Bang. Abstraction in description is therefore both necessary and inevitable. At some point even the most exhaustive account falls silent. The concept of absence then, like the concept of zero, is a tool that has proven to have enormous efficacy for us. Yet unlike the concept of zero, which is only ever acquired through education, there is evidence to suggest that human infants display an awareness of absence from a very early age and many animals also behave in ways that suggest a capacity to register absence.
Do these glimmerings constitute the rudimentary evidence of conceptual capacities, of proto-linguistic thought? Perhaps, but we should be wary. If we wish to provide a coherent causal theory of absence we will first need to explain the causal relations that lead to attributions of absence.
I have written previously of another philosopher, Anya Farennikova, who takes the view that we literally perceive absence. Farennikova contends that we possess mental states in which absences are represented. There is a serious problem with this theory though, and it is a difficulty reflected in the issues Pettersson brings to light. To assume that an inner representation represents absence requires this absence to have causal influence, thus violating the laws of causality.
The alternative is to view absence not as a causal entity of any kind but as the name we give to the common mismatch we find between what we expect and what we actually perceive. So, when we say that an infant or animal exhibits awareness of absence, what we really mean is that they are capable of forming expectations and of being surprised when these do not apply.
Absence is an enormously powerful and convenient concept, but the fact that we can treat such abstractions as concrete entities is no cause to invoke causality where none is possible. As far as images go, even the most explicit absence can only be recognised as such if we are capable of a contrasting expectation: of describing, delineating or selecting a substitute of that which is absent, of the actual presence envisaged.
Or, as Carl Sagan said (admittedly in a completely different context): "Absence of evidence is not evidence of absence."
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