Indirect realism is the view that the objects of perception are a mind-dependent representation which is caused by external mind-independent physical objects. Sense-data is perceived immediately (directly) whereas physical objects are perceived indirectly. The representation can be different from the object it represents. The argument from perceptual variation, illusion and hallucination, which try to show that what we see isn’t necessarily the reality, argue for indirect realism
Russell defines sense-data as the ‘content’ of our immediate sensory perception.
John Locke’s primary/secondary quality distinction
Locke claims that the objects of perception have primary qualities which are ‘intrinsic’ to the object and secondary qualities which are just in our mind. Primary qualities are shape, extension, number, movement. Secondary qualities are colour, taste, smell, touch.
Locke argues for this distinction by pointing to the case of a grain of wheat. If you continually divide a grain of wheat, eventually it will become insensible, having no colour, taste, smell or touch. However, it will still have a shape, extension, number or movement. This shows that secondary qualities are separable from an object, whereas primary qualities are not.
Indirect Realism issue: Scepticism about the existence of mind-independent objects
Indirect realism claims that the objects of perception are mind-dependent sense data that represents and is caused by mind-independent objects.
However, if all we perceive directly are sense-data, then we never perceive the mind-independent objects which Indirect realists claim are giving rise to and being represented by that sense-data.
There is a ‘veil of perception’ between our sense data and the external world through which we cannot perceive. In that case, it seems we can’t actually know that mind-independent objects exist at all, let alone whether sense data represents them.
For example, solipsism could be true; that only my mind exists and my perceptual experience is caused by my imagination.
Integration: The first claim of indirect realism, that the objects of perception are mind-dependent sense data, undermines our ability to justifiably know the second claim, that sense data is caused by and represents mind-independent objects. So, direct realism is epistemologically self-defeating and we can never be justified in believing it.
Russell’s best hypothesis response to the issue of scepticism
Russell argued we can neither prove nor disprove either the claim that the external world exists and causes my sense data, or the claim that the external world does not exist and so does not cause my sense data. Since we cannot prove for certain either claim, we are left with making a hypothesis (a theory which is confirmed or disconfirmed by experience or reason). Russell argues the question then becomes which possibility – that the external world exists or does not – is the best hypothesis.
Russell points to the example of a cat. When first you glance, it is in a corner of the room. The next time you look, it is on a sofa. If there is no external world, then the cat just disappeared from one place in perceptual experience and then appeared in another. However that does not provide an explanation of the experience as there is no reason why that should happen. If we take the other hypothesis, that there is an external world so the cat is a mind-independent object which continues existing when unperceived, then we have an explanation of our sense data of the cat having moved to the sofa – it walked there when you weren’t looking! Since this hypothesis actually explains our experience, it is the better explanation and so, Russell concludes it is the best hypothesis.
However, Russell’s argument can be responded to. Why is the cat having its own mind-independent existence really a ‘better’ explanation of our experience? What criteria is Russell using to judge that? It makes more sense ‘to us’, but that could just be because of our habit of thinking that there is an external world. If we discount that, it’s hard to see what possible reason we could have to prefer Russell’s explanation to the explanation of solipsism – the view that only our mind exists and the physical world does not. Both explanations are equally consistent with any and all experience, therefore there is no justification to prefer either and thus no way to say which explanation is better, so Russell’s ‘best hypothesis’ argument fails.
John Locke’s argument from the involuntary nature of our experience
Locke argues that perceptions from sense experience have a key difference to perceptions from memory or imagination in that we have no choice over what we perceive in sense-data. However, we can choose what to remember or imagine. If there really were no external world causing our sense-data, then everything must be in our mind. In that case, we should expect to have choice over perceptions from sense experience. However we do not – if we look at a bottle of water we have no choice but to see one. Yet if we want to imagine a bottle of water filled with gold or remember the last time we drank from one, we can. Since we have choice over perceptions which originate from our mind yet we have no choice from those from sense experience, it follows that perceptions from sense experience do not originate from our mind but from an external world.
The argument from the coherence of various kinds of experience (Locke & Cockburne)
Locke also argues that sense-data from different senses back each other up. E.g if I see an apple, I can touch it to see if it also feels like one, and taste it to see if it also tastes like one.
Locke combines these two arguments in the example of changing how paper looks by writing on it – so sight and the sense of your hand moving cohere. You cannot cause the words to appear on the paper by mere imagination, you have to actually write. Once it is written, it cannot be changed except by further writing. If someone else read out what you had written, there would be coherence between your auditory (hearing) sense-data and what you thought to write. Lock argues this ‘leaves little reason for doubt’ that there is an external world.
Catherine Cockburn also responds to scepticism about the existence of mind-independent objects with an argument from experiential coherence. She first points to the radical difference between experiences gained from different senses. E.g. The sound a waterfall makes is not just different to but of a very different sort than the visual experience of it. Cockburn then points out we learn to pair visual and auditory experiences together such that we are able to make an inference from one to the other. If we are walking on a mountain and hear a waterfall, we can infer and accurately predict what it looks like; and vice versa, if we see a waterfall from far away, we can infer and accurately predict what it will sound like when we have moved closer. The fact that we can accurately infer and predict our experiences suggests that there is some mind-independent object which both senses perceive yet is independent of any particular sense. If it could be heard without being seen and seen without being heard, then it seems to follow it exists without being seen or heard, i.e. mind-independently.
Arguably however Locke hasn’t proven that there is an external world of physical objects, he has merely given some reasons as to how it makes sense of our sense-data for there to be one. Locke claims the fact that we have no choice over our sense-data perceptions shows they are not a part of our mind. However, this is to assume all parts of our mind are under our control. There might be some reason unknown to us why sense-data originating from our mind isn’t under our control. There might also be some reason why we get the same information from different senses, despite them also potentially originating from our mind.
Nonetheless, indirect realism can still be justified by Locke’s arguments if we use Russell’s notion that it is the best hypothesis. The existence of the external world is the best explanation of lack of choice over perceptions and the coherence of various senses.
The argument from Berkeley that we cannot know the nature of mind-independent objects because mind-dependent objects cannot be like mind-independent objects
Indirect realism relies on the claim that our perceptions are mind-dependent sense data which represents mind-independent objects. Berkeley attacks this claim with the likeness principle, which states that to justifiably say that two things to be alike, they must be comparable. But, ideas (mind-dependent) can only be compared to other ideas. There is no way to compare ideas to mind-independent objects and so resemblance between them cannot be justifiably claimed.
Integration: this issue attacks the claim of indirect realism that the objects of perception represent mind-independent objects.
An indirect realist can respond that Berkeley assumes that representation requires resemblance. Arguably there are other methods of representation. For example, the symbols we use in language are completely arbitrary, meaning they have no resemblance to the objects they refer to. The word ‘chair’ does not resemble a chair but nonetheless can represent it. So, mind-dependent objects can be ‘like’ mind-independent objects if we take ‘like’ to involve representation without resemblance.
However, we could defend Berkeley by taking his argument to not be attacking whether an idea could be like a mind-independent object, but whether we could ever be in a position to know that it does. Berkeley seems to be saying that in order for a person to know that an idea is like a mind-independent object, they would have to compare them, yet that cannot be done since we have no direct perception of mind-independent objects. So, no one can justifiably claim that ideas represent mind-independent objects and therefore indirect realism cannot be justified.
Even if we restrict ‘likeness’ to representation, nonetheless our perceptions might not even represent the mind-independent world. It could be totally unlike our perceptions in any respect.
So, we just cannot know whether our perceptions represent mind-independent objects. Indirect realism leads to this sceptical issue, therefore.