One aspect of "outside books" ספרים חיצונים that is hard to understand is that the way the Rif and Rosh understand it, it refers to books that create their own explanations of verses of Torah than are not from the Gemara or midrash. If we would accept this literally there is no book in the religious world that would be allowed to read. All of them come up with explanations of verses that are not from the Gemara or midrash.
Background In the Mishna in Sanhedrin there is a list of things for which one loses his portion in the next world. "Reading outside books" ספרים חיצונים is on the list. The Rif and Rosh explain that refers not to science, but rather books that explain the Torah-- but in ways other than what is in the Gemara. The issue is not that they are saying things against Torah. The whole point is that it is pseudo Torah. As long as it is not from the sages it is by definition Torah of the Dark Side. This would mean almost all books in the religious world nowadays.
[The issue is maybe not as important as another more serious issue: worship of people. Why is it that in the religious world this is thought to be OK I am not sure.]
Background In the Mishna in Sanhedrin there is a list of things for which one loses his portion in the next world. "Reading outside books" ספרים חיצונים is on the list. The Rif and Rosh explain that refers not to science, but rather books that explain the Torah-- but in ways other than what is in the Gemara. The issue is not that they are saying things against Torah. The whole point is that it is pseudo Torah. As long as it is not from the sages it is by definition Torah of the Dark Side. This would mean almost all books in the religious world nowadays.
[The issue is maybe not as important as another more serious issue: worship of people. Why is it that in the religious world this is thought to be OK I am not sure.]
