Here: http://www2.cms.hu-berlin.de/newlogic/webMathematica/Logic/FOLDECISION2.pdf Timm Lampert claims to refute the Church-Turing theorem that first-order logic is undecidable. I'm wondering where the first error is!
Perhaps it would help Thomas Andrews if I gave references to where the unsolvability of the Entscheidungsproblem was first demonstrated. (Though I had supposed this was well known.)
Church, 1936a: 'An unsolvable problem of elementary number theory', American Journal of Mathematics, 58: 345-363.
Church, 1936b: 'A note on the Entscheidungsproblem ', Journal of Symbolic Logic, 1: 40-41.
Turing, 1936: 'On computable numbers, with an application to the Entscheidungsproblem, Proceedings of the London Mathematical Society, 42: 230-265.