John Locke:

An Essay Concerning Human Understanding (Book IV)

If information goes into your brain via your senses, how can you be sure that this information comes from an actual object?

Background

In the final book of An essay Concerning Human Understanding, John Locke attempts to defend his vision from objections. The main objection is that, if Locke is right, the external world may not be real - we may be plugged into a virtual reality, a kind of matrix.

A summary of the first three books

Locke's project is to establish how we learn things, and how we find things out.
In book I, he argued that we are not born with innate knowledge, instead we acquire it throughout our lives.
In book II, he argued that we experience the world indirectly via our senses. That things were made of atoms that we cannot see, but they have the power to bring about certain sensations in us.
In book III, he argued that communication is when we transmit our private ideas from our minds to that of someone else, and that the meaning of a word can be giving by a checklist of features and part of science's job is to improve that checklist.

The objection that Locke's conception of the mind leads to scepticism about the existence of mind-independent objects

Locke realised that his vision of the mind might lead to some serious problems. According to his view, we receive information from the outside world (from atoms) via our senses -light bounces of atoms and enters our eyes, for example. Therefore, we don't directly experience atoms. Could it not be the case that this information is being directly pumped into our brains? How do we even know that we have eyes?

This was the argument that Locke wanted to discuss in book IV.

(Nowadays, we call the information that we recieve via the senses sense-data.)

(Assuming) sense data are ‘private’.
(Assuming) we can only know what we perceive directly
According to indirect realism, we are directly aware only of sense-data, and must infer the existence of objects beyond the mind.
But, it is conceivable that our sense-data do not correspond with any material reality. (Perhaps we are living in the Matrix.)
∴ we can't be sure that the sense-data comes from actual atoms.

Locke’s argument from the involuntary nature of our experience

One of Locke's responses to this objection is the idea that our experiences are involuntary, and therefore cannot be caused by us.

An idea is mind-dependent if it is produced in my mind. It is mind-independent

If perception were mind-dependent (produced in my mind), then I could choose what I experience.
Perceptual experiences cannot be chosen
In perception, I cannot avoid having certain sense-data ‘produced’ in my mind.
By contrast, if I turn from perception to memory or imagination, e.g. by shutting my eyes, I find that I can choose what I experience.
∴ Perceptual experiences – which ‘I have whether I want them or not – must be produced in my mind by some exterior cause’.

The argument form the coherence of various kinds of experience

Another of Locke's defences is that our experiences all seem to make some kind of sense. What we see coheres with what we hear, and what we see from one day coheres with what we see from the next.

If our different senses ‘confirm’ the information that each supplies (if they cohere), then they must be caused by something mind-independent.
Some experiences do confirm each other
∴ Some of my experiences must be caused by something mind-independent. E.g. If I see a fire and doubt whether it is real, I can confirm its reality by touching it.

Discussion

Does the first argument prove that the external world exists? Could it not be the case that we are a brain in a VAT or a character in a computer game? If we lived in a computer game, would we be able to control our experiences?

Does the second argument prove that the external world exists, or only make it a plausible belief? Could it be the case that everything just happens to cohere?

Discussion

Is the aim of philosophy just to state the obvious?

In this passage, Gilbert Ryle writes that John Locke's most important contribution to philosophy is something like, 'the more secure your evidence, the more secure your belief'. He says that some people will criticise this by saying that it's obvious. But Gilbert Ryle replies by saying that this is precisely the aim of philosophy -to make things obvious that weren't.

I can imagine that some of you may grumble: ‘Then did Locke’s great contribution just amount to his long-winded statement of the obvious truth that the tenacity with which people hold their opinions is not always, but ought always, to be proportioned to the quantity and quality of the reasons that can be adduced for them?’ To this grumble I reply, ‘Yes, yes, yes!—but who made this obvious if it was not John Locke?’ Every philosopher of genius has made obvious to mankind things that, in his youth, had not been more than, if as much as, quaint speculations. Every philosopher of genius can be ridiculed for having once painfully excogitated and laboriously argued positions which we absorbed effortlessly with our mother’s milk. This is their contribution. They, with sweat and worry, designed and laid the pavements on which we easily stroll. Our difficulty is that of re-discovering what on earth it was that prevented them from strolling on these good, old pavements. The idea that there was a time, namely their time, when these pavements were missing is an idea to which, precisely thanks to them, we are not accustomed. To his pupils their teacher, if he is any good, is always the sedulous transmitter of the obvious. Its obviousness is his gift to them. How could they discern behind the ease of their reception of it, the pains that had gone to his giving of it? Standing on his shoulders, they cannot conceive why his feet had not from the start been where theirs are now.

Tasks

Explain the objection against which John Locke was defending his ideas.
Explain his defence from the involuntariness of experience.
Explain his defence from the coherence of experience.
Evaluate John Locke's defences. Are they convincing? Explain your answer.
What do you think of John Locke's project overall?

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