 Avicenna himself adverted to the problem of whether or not Categories was a properly logical book, and decided that it was not, though he treated it in the Cure out of deference to Peripatetic custom. His arguments for deeming it not to be properly logical have been gathered together in the past (see esp. Gutas 1988: 265–267), but the line of argument had already been stated neatly by later logicians. Here is Hillî dealing with why Tûsî moves from the five predicables (or “five categories”) to the ten categories: