http://popups.lib.uliege.be/1373-5411/index.php?id=4351 This paper discusses the presence of undecidable problems in mathematics, with reference to the halting problem for algorithms, the hypergame paradox and the paradox of the well-founded sets. All these results are curiously related to self-reference and the strange loop by which a self-observing system can indicate its own operations to itself. Full text issues Volume 28 Introduction : Lecture of CASYS Award fr Thu, 10 Oct 2024 10:00:14 +0200 Thu, 10 Oct 2024 10:00:32 +0200 http://popups.lib.uliege.be/1373-5411/index.php?id=4351 0