The subject is confronted with the evidence that his wife is also his mother, and additionally with the fact that this GLUT predicts he will do X.

In what situation does the GLUT predict that he will do X? Let's say, for example, that the GLUT predicts: "Confronted with the evidence that his wife is also his mother, the subject will do X." When the subject is confronted with the evidence, and also with the GLUT's prediction, he does Y. But the GLUT is not wrong, because it predicted his actions under a different set of information than he actually had. Alternatively, let's define A as: "evidence that his wife is also his mother, and that when shown evidence A, does X". There is no particular reason that there has to exist an X such that it is possible to construct A.