 A question in regard to which Bolzano adopted an especially interesting position was the problem of miracles. According to the traditional view, they are supernatural events or even immediate effects of God. Sometimes this is understood in the sense that miracles are events which are not explainable by means of the laws of nature or even incompatible with these laws. This view, however, has to face serious problems as Bolzano has painfully made clear (cf. RW I, 422–439, especially 424–436). Bolzano rejects these definitions mainly for the following reason: “If by the laws of nature one here meant laws a priori, no divergence from them would be possible; if, by contrast, one meant empirical laws of nature, a departure from these is nothing but what has been called an unusual occurrence” (RW I, 436). Being an “unusual occurrence” is on Bolzano’s own view a necessary (though not a sufficient) characteristic of a miracle (RW I, 437). An unusual event, however, is simply an event that is improbable (RW II, 68), hence an event whose intrinsic probability is \(\lt \bfrac{1}{2}\) (Bolzano 1838, 383). It can happen, however, that in every possible explanation for a fact certain unusual events would have to be presupposed, and that in such a case the assumption of a miracle, of which we receive a report, is the least improbable and consequently the most probable explanation (RW II, 69). Such circumstances do not, however, detract from the divinity of miracles and revelation but rather can have certain advantages, for these miracles thus become credible (RW I, 441 f.).