Perception as a Source of Knowledge
What do we need to know for this topic?
This is still a part of the Epistemology unit. So for this topic, we are looking at how we gain knowledge via perception. The theories we need to know are: Direct Realism, Indirect Realism and Idealism.
Direct Realism
The immediate objects of perception are mind-independent objects and their properties
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Direct realism (or naïve/common-sense realism) is the view that physical objects exist independently of our minds and are perceived directly.
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Objects exist objectively in space and time, so if I leave a room, they continue to exist and maintain their properties unless physically altered.
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Our senses give us direct access to these objects and their properties, such as a Willow's (my dog, above) color, shape, size, smell, and texture.
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There is no mediation between the perceive and the object, you see things exactly as they are in the mind-independent world.
Problem: Perceptual Variation
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Bertrand Russell argued that what we perceive is not the same as what is in reality and so direct realism is false. Look at a shiny, brown table. He argues that the color of the table actually depends on where you stand in relation to it.
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There is light falling on the table making a part of it shiny and therefore white in color in a certain spot, but if another person were to stand at a different place to you, that white spot would appear to them to be on a different part of the table than where it appears to you.
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Therefore, where one person sees the table to be white, another might see it to be brown. A particular spot on an object cannot be two colours at once, therefore colour cannot be a property of the table.
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Image on the left shows the 'Dress' that went viral a few years ago. People can't quite agree on its colour demonstrating a variation in perception.
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Integration (what is this attacking specifically?): the properties we perceive are properties of a mind-independent object. Our perceptions must be mind-dependent sense data instead of direct perception of mind-independent objects.
Problem: Illusions
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If you look at a straight stick submerged in a glass of water, refraction makes it look bent.
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An illusion occurs when an object (the stick) appears to have a property (of bentness) yet in reality it does not have that property (It isn’t bent).
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Therefore, the perceived illusory property is sense data which exists in the mind, not reality.
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Illusions appear just as real as normal veridical perceptions – they are subjectively indistinguishable.
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Therefore, normal perceptions must also be of sense data in the mind, not of physical objects. So direct realism is false.
Problem: Hallucinations
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Hallucinations occurs when perceiving an object that doesn’t exist.
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Therefore, what we perceived must be mind-dependent sense data.
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Hallucinations are subjectively indistinguishable from normal veridical (true) perceptions, therefore normal perceptions must also be of sense data, not mind-independent physical objects.
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So direct realism is false.
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Potential Response: The disjunctive theory of perception holds that perception can take one of two mutually exclusive forms: veridical perception or hallucination. Hallucinations involve the mind being disconnected from reality, whereas veridical perception involves direct contact with it. Although hallucinations and veridical perceptions may appear the same, they are fundamentally different. Therefore, the existence of hallucinations does not imply that all perceptions are mind-dependent.
Problem: Time Lag
Earendel is a star that is currently
28 billion light-years away. That means that if we were to look at it, we would see it as it was 28 billion years ago
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It takes time for light to reach us from an object we perceive.
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E.G. The light from the stars we see in the sky may have taken millions of years to reach earth. So we see those stars as they were millions of years ago, not as they are now.
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Although the objects of perception we more regularly see are much closer, like a table or chair, the light still takes some time to reach us.
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Therefore, we are not seeing the objects of perception directly, we are seeing them as they were in the past and therefore, direct realism is false.
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Potential Response:
The direct realist can argue that this response confuses what we perceive with how we perceive it. Yes, we perceive objects via light and sound waves and, yes, it takes time for these light and sound waves to travel through space. But what we are perceiving is still a mind-independent object (it’s not sense data or some other mind-dependent thing) – it’s just we are perceiving the object as it was moments ago rather than how it is now.
Indirect Realism
Objects of perception are a mind-dependent representation which is caused by external mind-independent physical objects
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The external world exists independently of the mind. There IS an external world.
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However, perceive the external world indirectly, via sense data (mind-dependently)
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Sense-data is perceived immediately because it is immediately accessible to us, but physical objects are perceived indirectly.
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The representation can be different from the object it represents.
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The argument from perceptual variation, illusion and hallucination try to show that what we see isn’t necessarily the reality.
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Bertrand Russell defines sense-data as the ‘content’ of our immediate sensory perception.
John Locke’s primary & secondary quality distinction
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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.
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Locke uses the example 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.
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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.
Problem: Is there an External World?
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If all we perceive directly are sense-data (as claimed by IRs), then we never perceive the mind-independent objects themselves.
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There is a ‘veil of perception’ between our sense data and the external world.
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So how can we actually know that mind-independent objects exist at all? And how can we trust that our sense data are representative of them?
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For example, solipsism could be true; that only my mind exists and my perceptual experience is caused by my imagination.
Maybe we're in the matrix, maybe there is no external world at all, maybe we are a brain in a vat.
Because indirect realism says we only perceive sense data, it cannot then justify the claim that sense data correspond to real external objects. The view is therefore epistemically self-defeating.
Bertrand Russell - An Abductive Response to Scepticism
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Russell argued we can neither prove nor disprove either the claim that the external world exists and causes my sense data.
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Since we cannot prove for certain either claim, we are left with making a hypothesis.
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So, which hypothesis is better? 1. The external world exists, or, 2. The external world does not exist.
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Russell uses an 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 keeps despawning and respawning in various places.
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If we take the other hypothesis, that there IS an external world and 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. The cat probably walked around the room without us seeing.
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Since this hypothesis actually explains our experience, it is the better explanation and so, Russell concludes it is the best hypothesis.
John Locke - The Involuntary Nature of Perceptions
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Locke argues that perceptions from sense experience have a big difference to perceptions from memory or imagination in that we have no choice over what we perceive in sense-data.
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However, we can choose what to remember or imagine.
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If there really were no external world causing our sense-data, then everything must be in our mind and we should be able to choose what to perceive.
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However we do not – if we look at a bottle of water we have no choice but to see one.
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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.
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“when my Eyes are shut…I can at Pleasure re-call to my my Mind the Ideas of Light, or the Sun...But if I turn my Eyes at noon towards the Sun, I cannot avoid the Ideas, which the Light, or Sun, then produces in me...And therefore it must needs be some exteriour cause...that produces those Ideas in my Mind.” - Locke
John Locke - The Coherence of Our Sences
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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.
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Locke combines this idea with the argument from above. Think of having a blank piece of paper in front of you, can you create words on the page and see them without doing anything?
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You cannot cause the words to appear on the paper by mere imagination, you have to actually write.
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If someone else read out what you had written, there would be coherence between what you hear and what you thought to write. Lock argues this ‘leaves little reason for doubt’ that there is an external world.
This is supported by Catherine Cockburn who argues from experiential coherence: different senses give us radically different kinds of experiences. For example, the sound of a waterfall is nothing like its visual appearance. Yet we learn to reliably pair these experiences, allowing us to infer one from the other. This cross-sensory prediction suggests a single mind-independent object underlying both experiences.
Problem: Does this actually defeat the sceptical challenge?
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The information you hear, see, feel etc may be equally misrepresentative of the external world.
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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.
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It assumes all parts of our mind are under our control.
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Locke's argument doesn't solve the problem of Indirect Realism of whether there is actually an external reality.
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However, Russell's 'best explanation' theory still justifies Indirect Realism.
Problem: Berkeley - Mind-independent objects aren't comparable to mind-dependent ones.
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This will lead into Idealism. To get the foundational idea of Idealism, we start by criticising the notion of mind-independent objects.
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Indirect realism claims that what we are immediately aware of in perception are mind-dependent sense-data, and that these sense-data represent or resemble mind-independent physical objects.
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Berkeley challenges this using the Likeness Principle which states that for two things to resemble one another, they must be of the same kind and comparable in nature (same ontological status). For example, a picture can resemble another picture, or a sensation can resemble another sensation, because they share a common type of existence.
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However, Berkeley argues that ideas (sense-data) can only be compared with other ideas. Since ideas are mental, and physical objects are non-mental, there is no possible point of comparison between them.
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We can never step outside our own ideas to check whether they accurately resemble an external, mind-independent world. Therefore Indirect Realism's central claim, that sense-data represent or correspond to physical objects, is unjustified.
Idealism
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The immediate objects of perception (ie ordinary objects such as tables, chairs, etc) are mind-dependent objects.
Fun fact: Berkeley pushed the selling of something called "tar-water" (which is exactly what it sounds like) as a cure all to get rid of "strong spirits".
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Idealism is the view that: There is no external world independent of minds (so it rejects realism – both direct and indirect)
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We perceive ideas directly
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Berkeley argues that the only thing our senses perceive are qualities, and nothing more.
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So, Berkeley and Locke do seem to agree that secondary qualities are mind-dependent but where they disagree is that Berkeley thinks that primary qualities are also mind-dependent (size can very on your whereabouts etc).
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Realism is fake, everything is mind-dependent and implies that there is no external mind-independent world.
Justification for Idealism - The Master Argument
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Philonous: Let’s test your belief in mind-independent matter. You think objects can exist outside any mind, unperceived?
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Hylas: Yes, of course. A tree, for example, could still exist even if no one were looking at it.
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Philonous: Very well. Try to conceive of such a tree, a tree existing entirely unperceived by any mind.
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Hylas: I imagine a tree standing in an empty forest, with nobody around.
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Philonous: But notice what you’ve just done. The tree you are imagining, where is it?
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Hylas: In my mind. It is an idea I’m picturing.
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Philonous: Exactly. Whenever you attempt to conceive of an object that supposedly exists outside all minds, you can only do so by forming an idea in your own mind. So the very act of trying to imagine a mind-independent object makes it mind-dependent again.
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Hylas: So I cannot conceive of something existing unconceived?
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Philonous: Precisely. To conceive of an unconceived tree is a contradiction. Since we cannot even form a meaningful idea of a mind-independent object, the notion of “material substance” is unintelligible.
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Hylas: Then matter, as I understand it, cannot exist.
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So what does this prove? The Master Argument says that we cannot even conceive of a mind-independent object because as soon as we conceive of such an object, it becomes mind-dependent. Thus, mind-independent objects are impossible.
Berkeley's Claim that God is the Cause of Perceptions
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If everything we perceive is mind-dependent, what is the cause of these perceptions? We know it is not an external world, because the Master Argument shows why that is not the case.
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We are left with 3 possible causes:
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Ideas
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My own mind
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Another mind
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It can’t be ideas, because ideas by themselves don’t cause anything.
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It can’t be my own mind, because I cannot control what I perceive
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Therefore, the cause of my perception must be another mind
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Given the complexity, variety, order, and manner of my perceptions, this other mind must be God
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Berkeley denies a mind-independent physical world but affirms that the world exists as a structured set of ideas sustained by God. Ideas are the whole substance of reality.
Esse est percipi (To be is to be perceived).
The existence of physical objects depends entirely on being perceived by a mind. Existence depends on a mind perceiving it, and God provides that constant perception so things don't just vanish when we stop perceiving them.
Problem: The Changing Nature of God?
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According to Berkeley, what we perceive are ideas that exist in God’s mind.
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However, if God is perfect he should not be able to feel the negative sensations that we do. EG: we often feel and perceive pain. So, if my perception of pain is an idea in God’s mind, surely God must feel pain too?
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Berkeley responds that ideas like pain exist in God’s understanding, but God doesn’t feel pain Himself.
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However, we can push this further. God is supposed to be unchanging (because change is an imperfection). Our perceptions are constantly changing. So, if my perceptions are ideas in God’s mind, and my perceptions are constantly changing, surely God must change too.
Problem: Illusions
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Idealism claims we perceive ideas directly as they are, because “to be is to be perceived.”
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However, think of the illusion of the stick-in-water example, we experience two perceptions at once. Both perceptions cannot equally reflect reality.
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At most, one of these properties can correspond to the actual stick, while the other must be an appearance. This shows a distinction between appearance and reality, implying that not all qualities of perception are simply what is perceived.
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Therefore, the claim that the existence of an object fully explained by its being perceived does not work, and Berkeley’s Idealism appears unable to account for the distinction between perceived properties and objective reality.
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Berkeley could respond to this: The stick ‘looking bent’ is correct, while ‘is bent’ assumes a mind-independent reality. Illusions only challenge theories that separate appearance from reality, which Berkeley does not do! For Berkeley, objects have no properties apart from how they are perceived.
Problem: Solipsism
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Solipsism is the view that one’s mind is the only thing that exists.
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And Berkeley’s earlier argument suggests that there is no reason to believe anything exists beyond one’s experience. If “to be is to be perceived”, then what reason do I have to believe other people and objects exist when I’m not perceiving them?
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If idealism is true, it seems to imply that nothing exists unless I am perceiving it; the world didn’t exist before I was born; the world doesn’t exist when I close my eyes or go to sleep. But this is surely absurd.
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This does not defeat Idealism, but it leads to epistemological scepticism which is something Berkeley said was a reason to not believe in Indirect Realism.
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Berkeley could respond: Even when no finite human mind perceives something, God perceives it. This ensures the continued existence and order of the world.
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However, we can criticise again by saying that Idealism's God just moves the question: it explains why objects exist when we don’t perceive them, but it doesn’t explain why God exists or why God perceives them in an orderly way. So it may seem like a circular argument.