Ayer, A.J (1971) "The Nature of Philosophical Analysis" Ch. 3. , pp. 59-68, of Language, Truth and Logic. London: Penguin. (Original work published in 1936)
For Ayer, logical-empiricism (reducing object-talk to experience-talk) involves a form of philosophical analysis that uses a technique called definitions in use
Explicit definitions = ordinary dictionary definitions that define a term in terms of others.
“We define a symbol explicitly when we put forward another symbol, or symbolic expression which is synonymous with it … [where] two symbols belonging to the same language can be said to be synonymous if, and only if, the simple substitution of one symbol for the other, in any sentence in which either can significantly occur, always yields a new sentence which is equivalent to the old.”
“when we define oculist as an eye-doctor, what we are asserting is that, in the English language, the two symbols “oculist” and “eye-doctor” are synonymous”
Definitions in use = defines a term by translating sentences in which the term occurs in such a way that the term no longer occurs in the translating sentences.
“We define a symbol in use … by showing how the sentences in which it significantly occurs can be translated into equivalent sentences, which contain neither the definiendum itself, nor any of its synonyms.”
Examples of definitions in use
There is a brown table in the living room
A logical empiricist will express the meaning of this sentence by translating it into other sentences that does not make reference to tables, but instead to sense contents.
part of the translation by a logical empiricist:
- in reference to the table = A brown patch occurs in a visual field
- in referent to the living room = The brown patch is situated in a broader visual array of such and such character.
- in reference to the sensation of touch associated with the visual sensations of the table = sense-contents of solidarity are present in the tactile vicinity of the brown patch
By translating sentences in which the term “table” gets reduced to verbiage that concerns sense-contents, we get a contextual definition of “table” that conveys the sense of the term as it operates in the context of complete sentences.
Ayer uses the term the given which means whatever is directly given to us in sense experience.
For logical empiricists like Ayer, material objects are just logical constructions out of sense-contents, or out of the “given”. The statements we make about material objects are logically equivalent to the statements we could make about sense-contents. The reduction goes via the logic of the language.
The problem of perception
Ayer describes the problem of perception (a version of the epistemological-gap-between-experience-and-theory) as the problem of reduction of material things to sense-content, i.e. the problem of giving an actual rule for translating sentences about a material thing to sentences about sense-content.
Problem of perception = if illusion and hallucinations are possible, how can perceptual experience provide us with direct perceptions of the world?1
Ayer notes that ordinary language isn’t good at precisely describing sense data and so, it is more convenient to talk about the world in the language of material objects instead. When we talk about material things, we are actually talking about sense-data in a more convenient, indirect way. In other words, to explain what a “material thing” is, we don’t have to point at something beyond experience, we just describe what kinds of relations our different sense experiences must have to count as experience of the same object (p. 65).
Ayer agrees with Humean-skepticism-about-the-external-world that what we directly know are sense-contents, not mind-independent objects. But instead of leaving it as a matter of psychological habit, Ayer gives this relationship a logical and linguistic reinterpretation.
Footnotes
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as defined by Stanford encyclopedia ↩