Abstract
One of the many important tasks of semantics is to provide an account of the substitution patterns of a language—that is, to furnish an explanation of the conditions under which semantic values of complexes are preserved when components are replaced. The importance of this issue is plain: we only have to recall the debates regarding substitutivity between proponents of direct reference theories and advocates of some version of Fregeanism, as well as the disagreements among different proponents of direct reference theories as regards substitutivity in belief reports.
This is why it is important to articulate an acceptable principle of substitution. A traditional statement of the principle of substitution holds that codesignative singular terms should be intersubtitutable salva veritate. In the past I have argued that such a principle is not connected properly to some pretheoretical data about the function of referring terms. In this chapter I argue that such a principle does not gain support either from other, more fundamental, laws. I end by defending the adequacy of a different principle of substitution.