 While many analysts (e.g., Wilson 1975, Atlas 1977, Gazdar 1979, Grice 1989) have since followed Russell by preserving a bivalent semantics and invoking pragmatic explanations of apparent presuppositional effects, other linguists and philosophers (e.g., Fodor 1979, Burton-Roberts 1989, von Fintel 2004) have defended and formalized theories of semantic presupposition in the Frege-Strawson spirit, allowing for the emergence of truth-value gaps or non-classical truth values when presuppositions are not satisfied.