Access to the full content is only available to members of institutions that have purchased access. If you belong to such an institution, please log in or find out more about how to order.


Print

Contents

Propositional attitude statements

DOI
10.4324/9780415249126-U030-1
DOI: 10.4324/9780415249126-U030-1
Version: v1,  Published online: 1998
Retrieved October 21, 2019, from https://www.rep.routledge.com/articles/thematic/propositional-attitude-statements/v-1

Article Summary

Propositional attitude statements – statements about our beliefs, desires, hopes and fears – exhibit certain logical peculiarities. For example, in apparent violation of Leibniz’s law of the indiscernibility of identicals, we cannot freely substitute expressions which designate the same object within such statements. According to Leibniz’s law, every instance of the following scheme is valid:

  • a = b

  • F(a)

  • Therefore, F(b)

The validity of Leibniz’s law seems beyond question. It says, in effect, that if an object has a certain property, then anything identical to that object also has that property. Valid instances abound. But consider the following apparently invalid instance:

  1. Hesperus is Phosphorus

  2. Hammurabi believed that Hesperus often rose in the evening

  3. Therefore, Hammurabi believed that ‘Phosphorus’ often rose in the evening.

If we take ‘Hammurabi believed that…often rose in the evening’ to serve as the predicate F and ‘Hesperus’ and ‘Phosphorus’ to be a and b respectively, this argument appears to be an instance of Leibniz’s law. Yet (3) apparently fails to follow from (1) and (2). Hammurabi believed that Hesperus and Phosphorus were two heavenly bodies not one. And he believed that Hesperus did, but that Phosphorus did not rise in the evening.

We have derived a false conclusion from true premises and an apparently valid law. If that law is really valid, then our argument had better not be a genuine instance of the law. The tempting conclusion, widely accepted, is that we were wrong to construe propositional attitude statements as simple predications. We should not, that is, construe ‘Hammurabi believed that…often rose in the evening’ to be just a long predicate with the semantic function of attributing some property to the object commonly denoted by ‘Hesperus’ and ‘Phosphorus’. But then the question arises: if attitude reports are not simple predications, what are they? Philosophers have disagreed sharply in their answers. Moreover, their disagreements are intimately connected to a wide range of deep issues about the nature of meaning and reference.

Print
Citing this article:
Taylor, Kenneth A.. Propositional attitude statements, 1998, doi:10.4324/9780415249126-U030-1. Routledge Encyclopedia of Philosophy, Taylor and Francis, https://www.rep.routledge.com/articles/thematic/propositional-attitude-statements/v-1.
Copyright © 1998-2019 Routledge.

Related Searches

Topics

Related Articles