So far, we have examined Russell’s theory of descriptions as a view about a particular class of expressions in English. We will now turn our attention to the importance of that theory for the philosophy of mind and epistemology. (Our discussion will be drawn from Russell’s ‘Knowledge by acquaintance and knowledge by description,’ in the coursepack.)
In ‘Descriptions’ Russell distinguished between names, which directly designate objects in the world, and definite descriptions, which do so indirectly. This gives us two ways in which the thought expressed by a sentence may concern an object: the object may itself be a part of the thought (as would happen if the sentence contained a Russellian name), or the object may be singled out indirectly by properties which are themselves a part of the thought (as would happen if the sentence contained a description satisfied uniquely by the object in question).
This distinction corresponds to an intuitive distinction between two ways of referring to, or thinking about an object. (Consider, on the one hand, demonstratives, and on the other hand, descriptions like ‘the point midway between my left foot and the surface of the sun’.)
This gives rise to a question: what kinds of objects can we think about directly, as opposed to merely indirectly, via some properties which they happen to have?
Given Russell’s view of names, we can raise this question in a linguistic form by asking, ‘What sorts of objects can we name?’
Our answer to this question will have a bearing on the philosophy of perception.
The first principle is about our access to our own thoughts:
| [1] | We can never be mistaken about whether or not we are thinking a thought. |
This is closely linked to another principle:
| [2] | One can never be mistaken about whether a sentence of one’s own language expresses a thought. |
These principles are linked because, you might think, if [2] were false then [1] would be as well. For if one could be mistaken about whether a sentence of one’s own language was meaningful, then one might say that sentence to oneself, thereby taking oneself to be thinking a thought. But if the sentence was meaningless, one would not be thinking a thought, and so one would, contra [1], be mistaken about whether one was thinking a thought. This is some reason to think that [1] entails [2].
Consider now the following plausible principle about the meaningfulness of words and sentences of which they are a part:
| [3] | If one expression in a sentence is meaningless, the sentence as a whole fails to express a thought. |
Consider, e.g., ‘They’re serving flibbertyflam in the cafeteria today.’ It’s plausible that this sentence fails to express a thought because ‘flibbertyflam’ lacks a meaning.
| [4] | The meaning of a genuine name is its reference. |
From [4], it is natural (though it does not strictly follow) to infer the following principle:
| [5] | If a name lacks a reference, it also lacks a meaning. |
But it follows from [3] and [5] together that
| [6] | Any sentence involving a name which lacks a reference fails to express a thought. |
But from [2] and [6] together it follows that
| [7] | One can never be mistaken about whether a name of one’s own language has a reference. |
From which it is natural to infer
| [8] | We can only understand names for objects about whose existence we cannot be mistaken. |
But now recall: Russell thought that there were two ways of thinking about objects, one direct (by acquaintance) and one indirect (by description). These two ways of thinking about objects correspond to two classes of linguistic referring expressions: genuine names, and descriptions.
This parallelism between thought and language suggests the following equivalence:
For all x (one can think directly about x iff one is acquainted with x iff one can understand a name for x)
If this is right, this means that we can derive from thesis [8] a claim about the sorts of objects with which we can be acquainted, or think directly about: those objects about whose existence we cannot be mistaken.
And from this it seems to follow that we cannot name, or be acquainted with, physical objects. (Russell states this conclusion on p. 214 of ‘Knowledge by acquaintance and knowledge by description.’)
This gives rise to two issues, one in the philosophy of language, and one in the philosophy of perception.
1. How are we to understand the thoughts expressed by sentences containing what seem to be names for ordinary material objects? Russell indicates that our knowledge of material objects ia always knowledge by description, so these names must be disguised descriptions. But what descriptions are they? Note what Russell calls the fundamental epistemological principle in the analysis of sentences containing descriptions: “Every proposition which we can understand must be composed wholly of constituents with which we are acquainted.” (p. 219) Given what we have learned about acquaintance, this seems to place severe restrictions on what sort of descriptions could give the meanings of these sorts of names.
2. If we are acquainted with anything, we are acquainted with the immediate objects of perception. But then the immediate objects of perception must not be material objects. So what are they?