[Another handout.]
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External World
Problem: How do we know that there is a world outside the mind?
I. Bishop George Berkeley: Immaterialism/Idealism
What do we really mean by ‘outside the mind’?
Isn’t the simplest way to answer the question to say that, strictly speaking, there is nothing outside the mind – everything is either a mind or something in a mind? (Get rid of ‘material substance’, the ‘unknown something’.) A reason to think this: primary and secondary qualities.
Bodies are then sensible ideas that our mind treats as going together. Note that this still means that bodies exist. Esse est percipi: To be is to be perceived.
But we take the world to be shared and independent of us in some way. How can it just be in our mind? Because it is coordinated by a higher mind. Divine language.
II. David Hume: Skepticism
It’s pointless to ask, “Whether bodies exist?” We all believe that they do. The question is, “Why do we believe they exist?” We will need to distinguish the causes of believing that bodies exist even when we don’t sense them (continued existence) and the causes of believing that they are distinct from perception (distinct or independent existence). They are connected, but it’s easier to see how they work if they are separated.
For the objects of perception to exist when we don’t perceive them is a contradiction (as Berkeley had noted). The senses can give us no notion of either distinct or continued existence. If our belief was based on reasoning, the reasoning would be too difficult. So it must be imagination that is the source of our belief.
All objects to which we attribute a continued existence have constancy and coherence.
The imagination attributes continued existence to uniform objects due to a mistake – it treats the perceptions as continuing to exist even when we aren’t perceiving because perceptions before and after the gap are so similar. With changing objects, it has a natural tendency to extrapolate (galley effect or mental inertia) to make our experience as regular as possible, and supposes that they continue to exist unperceived in order to do so.
Given continued existence, we naturally assume distinct existence. However, we can do experiments to show that perceptions can’t exist independently (we can modify them with our sense organs in such a way that we can’t tell which perceptions should be said to exist). Philosophers try to get around this by distinguishing perceptions and objects (the perceptions are interrupted but the objects continue); but the only reason why you would do so would be to save the assumption of continued and distinct existence, which we only believe because of the mistakes give above. Everyone, therefore, even philosophers, can do no more than oscillate between these two conflicting views.
III. Lady Mary Shepherd: Materialism
The problem really boils down to three things: external existence, continued existence, and independent existence. These are known by causal reasoning, not imagination.
The world ‘mixes’ with us; because this mixing introduces differences in us, we recognize that it is an effect. Therefore there must be a cause besides ourselves giving these sensations. Thus independent existence.
We get continued existence by discovering that these effects are ready to appear.
We get external existence by moving around, and therefore adding the idea of relation to motion.
We don’t know exactly what these external, independent, continued existences are, only that there must be something about them that gives the variety we experience.
Other Minds
The problem of other minds is very similar to that of the problem of the external world: How do we know that other minds exist?
Descartes’s answer: We know it because we find bodies exhibiting behavior (language and problem-solving) that can only be due to something capable of recognizing its own thinking (e.g., engaging in Cartesian meditation and reaching the cogito). A key question is whether this is adequate as an answer. It does seem to require rationalism rather than empiricism.
Another common answer (e.g., Bertrand Russell): We know in our own case that thinking causes certain behaviors. Sometimes we see the behaviors without the cause; therefore we infer that there is (probably) thinking we do not observe. (Argument from analogy.) An empiricist could easily accept this. One potential issue: analogy is a sliding scale, and the inference described here seems very ‘patchy’ and tentative compared to our actual views on other minds.
One question that comes up often, and gets answered in different ways: do we first know that other minds exist, or do we first know that external bodies exist? Which is more basic?
