Following on from the metaphysical theories of perception in the previous post, I next consider if perception is capable of providing us with knowledge. A second way of looking at the problem is to consider perception as part of the more general theories of epistemology (eg foundationalism). This approach will be considered in the next post.
The starting point for the metaphysical solutions is usually the sceptical argument, which claims (in the tradition of Descartes) that we can’t know anything at all about the mind-independent world. This would especially be the case if we consider all the usual scenarios where knowledge would be impossible, eg brain in a vat. In these cases, the sceptic argues that perceptual experience provides no evidence for reality.
The idea that we don’t know anything about an external world gives rise to a ‘veil of perception’. We might know a lot about our own internal perceptions, but we cannot be certain that the sensory organs are providing reliable information to begin with. And even if we can be certain, our knowledge of the external world can only be indirect at best.
The sceptical argument can be presented more formally as follows:
- The only thing present before the mind is perceptual experience
- We can only be justified with our perceptual beliefs if our experiences are ‘veridical’ (true to life)
- We have no reason for thinking that our experiences are veridical
- Therefore we are not justified in our perceptual beliefs
Basically, in order to prove our perceptual experiences are true, we must rely on perception to provide this evidence, which is clearly a case of begging the question.
One way to counter the sceptical argument is to show that we can obtain direct knowledge of the external world. In that way, we can dispense with the sceptical argument. The sceptic would insist that because our knowledge is only indirect (we can only be familiar with our own perceptions), we have no way of obtaining knowledge of the external world.
Some philosophers attempt to counter this by supporting a ‘direct realism’ approach (there is such a thing as a mind-independent world, and we can obtain direct knowledge of other objects), or by supporting idealism, which claims that the only things that exist are mental ideas, and this is something that we can be certain of. In other words, according to idealism, the perception of an object and the object itself is the same thing, so there is no gap that gives rise to scepticism. Even though direct realism and idealism are radically different ideas, they do agree on the idea that one can obtain genuine knowledge.
In terms of the specific theories of perception mentioned in the previous post, we can consider whether each theory gives rise to knowledge:
- Sense Datum: since sense datum is seen as a kind of internal impression (similar to an emotion or a feeling), they cannot be judged as either true or false. This gives rise to the obvious difficulty that we can obtain any knowledge of the external world if we can’t be certain of the veracity of our sense datum. The sense datum only provides an indirect view of the external world.
- Intentionalism: this is similar to sense datum in that experiences are mental images alone, so provide no direct evidence of the real world. The experiences might be representations of the real world, but these representations do not have the same properties as real objects, so knowing one gives you no evidence of the other.
- Direct Realism – unlike the other two theories above – which deal with mental images and indirect links to a mind-independent or hallucinatory world – direct realism suggests that perception creates a direct link to the objects in question. Because there is no gap between appearance and reality, the sceptical argument reduces in power. Direct realism takes one outside the world of the perceiver by proposing the direct link, meaning that the brain in the vat could never obtain perceptual knowledge (because, according to some theories, the brain in the vat lacks the causal connection to the real world). Therefore, because direct realism does provide a direct link, it is possible to refute the sceptical claim and obtain real knowledge.
- Disjunctivism – this is similar to direct realism, except with the two ‘strands’ of perception (one for the real world, and one for hallucinations). The real world strand would be interpreted in the same way direct world realism above.
We can also consider perception in terms of whether the link to the real world is direct or indirect. A number of theories have been proposed here:
- Phenomenal Directness: an experience is direct in the sense that it takes place without any inference or belief of behalf of the agent, that it, ‘it just happens’. This agent assumes that the agent had no choice in the matter.
- Referential Directness: perception provides us with a way to represent the external world, without the need for any other intermediary. However, this theory still needs to find a way how a representation can provide us with knowledge. In any theory where the link to the external world is indirect, we still can’t be certain of anything.
- Perceptual Directness: given that all we perceive is sense datum, our knowledge of the external world can only be indirect.
- Direct World Involveness: for the idealist, the perception of an object is equivalent to the object itself, in that both are mental images, so we can be said to have direct world knowledge. This is in contrast to hallucinations, which do not provide this direct link.
- Epistemological Directness: perception is a primary mental state that does not need to be justified. We can assume that all our perceptual beliefs are justified.