Dretske’s Dreadful Theory Of What We See

In a presentation from 2008, the late (as of 2013) Stanford philosophy professor Fred Dretske argues that seeing includes the perception of objects (including relations between objects), properties (shape, size and colour etc.) and facts. For Dretske, the facts we perceive are “things we come to know by seeing”. He claims that there is a danger that we take a failure to notice or detect objects and properties as a failure to actually see them. He presents the following two images in order to explain this claim.

Image A

Image B

Image B contains an additional shape. In his presentation, Dretske presents the images one after the other and inserts a transition between the two that makes it difficult to see the difference between them. In Dretske’s view: “One should not conclude from the fact that you didn’t see that there was a difference to the conclusion that you didn’t see the object that made the difference.” He remarks:

Even if you don’t detect it, even if you don’t notice it, even if you don’t know that you are seeing different things. Even if you don’t see the fact that there is a difference, you still might see the objects and properties that make the difference. You just don’t realise you do.

It should be obvious that if you do not detect, realise or notice that the traffic lights are red, then you cannot be said to see them (at least in respect of their being red). Nonetheless Dretske holds that seeing is independent of conscious awareness. In his view, we can genuinely see objects and properties without detecting, noticing or knowing that we do so. Dretske uses this questionable conclusion to promote his theory of conscious experience. He claims that: “Your experience of an object is conscious if it gives you knowledge of that object.”

For Dretske, all knowledge is knowledge of facts, and in order for an experience to be conscious, it must provide such knowledge. But this is absurd. If we look at a familiar object, we do not lose consciousness of it because it ceases to give us knowledge. If consciousness depends on the acquisition of knowledge, then all lapses in attention must be accompanied by lapses in consciousness. This is quite evidently not the case.

We perceive the phonemes, morphemes and sentences in which facts are typically stated but it is debatable whether we actually perceive facts at all. Earlier today I asked my partner “When did you last see a fact.” She looked at me quizzically and remarked: “You don’t see facts.” Some people might contend that texts, graphs and diagrams etc. can be seen and thus are visible facts, but it is important to note that representations of facts are not the facts they are used to represent. Many facts can be demonstrated, but it does not follow that a demonstration of a fact can be reduced to the fact it is intended to demonstrate.

Earlier in his presentation, Dretske states: “The facts we see—the things we come to know by seeing—we come to know them by seeing objects and their properties.” Clearly then, Dretske realises that perception of things is not the same as the “perception” (his use, not mine) of facts. Facts must be derived in some way from perception, but quite how they are derived Dretske neglects to mention.

The absurdity of Dretske’s position becomes more pronounced towards the end of his presentation. He argues that when we look at a wall of 350 bricks for a few seconds, we acquire 350 “distinct pieces of knowledge—one for each brick in the wall.”  Not only this, but during the Q&A session it becomes clear that he thinks we acquire “infinite” knowledge “for free” when we look at things. The reason he believes this is because he is committed to the idea that the perception of facts involves the acquisition of what he calls “tacit knowledge”.

You don’t have to actively think something to know it. There are a great many things you know tacitly, not because when you acquired the knowledge you are actually thinking about it or believing it but because you have the kind of experience of it which, if you do later think about it, will tell you what you need to know.

There is no such thing as a memory “telling” us anything, so Dretske can only mean that we have to interpret an experience ("later think about it") to derive factual knowledge from it. If we do not think about it—if we do not interpret the memory by means of our conceptually enabled inferential skills—then we cannot be said to have yet formed any factual knowledge on the basis of the memory. An analogy will help. If we have a workshop full of materials, we may be capable of using these to create some tools, but unless we actually manufacture these tools, we cannot claim to possess them. Tacit knowledge, and knowledge in general in fact, is not something that we possess like a scar or a souvenir, it is something we are capable of doing, something we are capable of bringing about by the application of skill.

When we fail to see a difference between two different things, at least two factors need to be taken into consideration. Firstly, our sensory organs may be limited by evolutionary constraints that give rise to regularly occurring fallibilities in certain circumstances. Secondly, the circumstances of encounter (the illumination, position, angle of view, delay between images etc.) may limit discrimination more than might otherwise be the case. Certainly any actual differences within our visual field may have a causal influence upon our sensory system, but this does not mean that these influences are dealt with at some non-conscious, unconscious or “sub-personal” (Dennett 1987) level of seeing that we "just don't realise". It just means that there are various complex processes involved in perception that are not conscious and that some of these have insufficient influence to rise to the level of purposeful action: consciousness.

At the 25:00 minute mark of the presentation, Dretske discusses an image of a square divided into nine coloured portions. He claims that if each of the nine squares was coloured the same shade of blue and placed so close together that we couldn't see the edges between them, we would still see nine squares. This is like arguing that we see the screen when we watch a movie. If pressed, we would probably agree that the screen is visible while we watch Star Wars or Gone With The Wind etc. But what we would be very unlikely to concede, and what follows from Dretske's thesis, is that we see each pixel on the screen and thus gain millions of distinct pieces of knowledge—one for each pixel. It should also be noted that pixels are themselves divisible into individual photons. Do we have distinct pieces of knowledge of photons too? 

At some point we have to acknowledge that all sensory systems are limited in various ways and it therefore follows that these limitations make it impossible to discriminate between things (that may in fact be quite different) in certain circumstances and in certain respects. It is by virtue of differences that all creatures discriminate between things. Without sensory discrimination there would be no life. Nonetheless, sensory discrimination is not free of limitations. Without these limitations, there would be no question of our mistaking any one thing for another different thing, and there would also be no question of our accepting a flat thing as a viable stand-in of a three-dimensional thing. The fact that things of one sort (images say) can be mistaken for things of another sort (three dimensional objects for example) makes images supremely apt as representational tools; as things that can stand-in for the objects they represent.

I suggest that any explanation of perception that fails to account for the role of discrimination failure within our practices of nonverbal representation is probably doomed.