The Early History of Formal Diagonalization.

The given text provides a comprehensive overview of the development and significance of diagonalization in mathematical logic. It discusses the contributions of various mathematicians and highlights the use of self-reference and provability logic in diagonalization. The text also mentions the avoidance of diagonalization in certain proofs and the exploration of modal logic of provability. It concludes by mentioning the contributions of Solovay and the generalization of diagonalization. The author also references their own book on self-reference and modal logic. [Extracted from the article]