  In this book, Crescas deals with the subject of free will in a less profound manner than in his philosophical magnus opum Or Hashem, but his opinions here do not contradict his opinion in Or Hashem. The difference between the two books on this subject can be attributed to the development of the thought of Crescas.  According to one view, the sermon represents an anterior stage of Crescas and Or Hashem a posterior one (Sermon on the Passover, pp. 34–68).  Another explanation of these differences could be the difference of style between the two books (a sermon versus a profound philosophical tract). The difference between the two books is clearer with regard to the question of the essence of miracles.  Crescas’s opinion in his sermon is that miracles by themselves don’t oblige people to believe in something (as opposed to rational proofs that oblige belief). The reason for inherent doubt in the validity of any given miracle is that the people cannot be sure that God and not a human is the author of the miracle. In Or Hashem (P. 312) Crescas asserts the opposite position. Humans cannot do miracles by  themselves.[6] This is the reason that Crescas claims that the miracle is the best way to verify if a prophet is a true one or an  impostor.[7] This difference between the two works is a very good argument for the opinion that the sermon is anterior to Or Hashem. Ravitzky has said that in the sermon, Crescas followed the ideas of Rabbi Nissim Girondi, his teacher who believed in the possibility of men performing miracles, while years later, in Or Hashem, Crescas retreated from this opinion and now held that only God could perform miracles.