Donkey sentence

Donkey sentences are sentences that contain a donkey pronoun or donkey anaphora. Such pronouns or anaphoric expressions may also be called d-type or e-type pronoun, depending on theoretical approach to interpretation.

A donkey pronoun is a pronoun that is bound in semantics but not syntax.[1][2] Some writers prefer the term "donkey anaphora", since it is the referential aspects and discourse or syntactic context that are of interest to researchers (see anaphora).

The following sentences are examples of donkey sentences.

Such sentences are significant because they represent a class of well-formed natural-language sentences that defy straightforward attempts to generate their formal language equivalents. The difficulty is with understanding how English speakers parse the scope of quantification in such sentences.[3]

Peter Geach's original donkey sentence was a counterexample to Richard Montague's proposal for a generalized formal representation of quantification in natural language. The example was reused by David Lewis (1975), Gareth Evans (1977) and many others, and is still quoted in recent publications.

Features

Features of the sentence, "Every farmer who owns a donkey beats it," require careful consideration for adequate description (though reading "each" in place of "every" does simplify the formal analysis). The donkey pronoun in this case is the word it. The indefinite article 'a' is normally understood as an existential quantifier, but the most natural reading of the donkey sentence requires it to be understood as a nested universal quantifier.

There is nothing wrong with donkey sentences: they are grammatically correct, they are well-formed, their syntax is regular. They are also logically meaningful, they have well-defined truth conditions, and their semantics are unambiguous. However, it is difficult to explain how donkey sentences produce their semantic results, and how those results generalize consistently with all other language use. If such an analysis were successful, it might allow a computer program to accurately translate natural language forms into logical form.[4] The question is, how are natural language users, apparently effortlessly, agreeing on the meaning of sentences like these?

There may be several equivalent ways of describing this process. In fact, Hans Kamp (1981) and Irene Heim (1982) independently proposed very similar accounts in different terminology, which they called discourse representation theory (DRT) and file change semantics (FCS) respectively.

In 2007, Adrian Brasoveanu published studies of donkey pronoun analogs in Hindi, and analysis of complex and modal versions of donkey pronouns in English.

Discourse representation theory

Donkey sentences became a major force in advancing semantic research in the 1980s, with the introduction of discourse representation theory (DRT). During that time, an effort was made to settle the inconsistencies which arose from the attempts to translate donkey sentences into first-order logic.

Donkey sentences present the following problem, when represented in first-order logic: The systematic translation of every existential expression in the sentence into existential quantifiers produces an incorrect representation of the sentence, since it leaves a free occurrence of the variable y in BEAT(x.y):

\forall x\, (\text{FARMER} (x) \and \exists y \,( \text{DONKEY}(y) \and \text{OWNS}(x,y)) \rightarrow \text{BEAT}(x,y))

Trying to extend the scope of existential quantifier also does not solve the problem:

\forall x \,\exists y\, (\text{FARMER} (x) \and \text{DONKEY}(y) \and \text{OWNS}(x,y) \rightarrow \text{BEAT}(x,y))

In this case, the logical translation fails to give correct truth conditions to donkey sentences: Imagine a situation where there is a farmer owning a donkey and a pig, and not beating any of them. The formula will be true in that situation, because for each farmer we need to find at least one object that either is not a donkey owned by this farmer, or is beaten by the farmer. Hence, if this object denotes the pig, the sentence will be true in that situation.

A correct translation into first-order logic for the donkey sentence seems to be:

\forall x\, \forall y\, ((\text{FARMER} (x) \and \text{DONKEY}(y) \and \text{OWNS}(x,y)) \rightarrow \text{BEAT}(x,y))

Unfortunately, this translation leads to a serious problem of inconsistency. One possible interpretation, for example, might be that every farmer that owns any donkeys beats every donkey. Clearly this is rarely the intentional meaning. Indefinites must sometimes be interpreted as existential quantifiers, and other times as universal quantifiers, without any apparent regularity.

The solution that DRT provides for the donkey sentence problem can be roughly outlined as follows: The common semantic function of non-anaphoric noun phrases is the introduction of a new discourse referent, which is in turn available for the binding of anaphoric expressions. No quantifiers are introduced into the representation, thus overcoming the scope problem that the logical translations had.

See also

Notes

  1. ↑ Emar Maier describes donkey pronouns as "bound but not c-commanded" in a Linguist List review of Paul D. Elbourne's Situations and Individuals (MIT Press, 2006).
  2. ↑ Barker and Shan define a donkey pronoun as "a pronoun that lies outside the restrictor of a quantifier or the antecedent of a conditional, yet covaries with some quantificational element inside it, usually an indefinite." Chris Barker and Chung-chieh Shan, 'Donkey Anaphora is Simply Binding', colloquium presentation, Frankfurt, 2007.
  3. ↑ David Lewis describes this as his motivation for considering the issue in the introduction to Papers in Philosophical Logic, a collection of reprints of his articles. "There was no satisfactory way to assign relative scopes to quantifier phrases." (CUP, 1998: 2.)
  4. ↑ Alistair Knott, 'An Algorithmic Framework for Specifying the Semantics of Discourse Relations', Computational Intelligence 16 (2000).

References

Further reading

External links

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