Non sequitur

From Yiftach J.H. Fehige,'Thought experimenting with God. Revisiting the Ontological Argument' in Neue Zeitschrift für Systematische Theologie und Religionsphilosophie, 51 (2009) 249–267: 'it makes sense that Anselm of Canterbury offered his versions of the ontological argument in the form of a prayer, which, presupposing the existence of god [sic], seems to run counter to a proof of god's [sic] existence.'

Presumably in much the same way that Newton's belief that apples would fall ran counter to his work on the law of gravity.