 Number plays an epistemological role; it is what allows things to be known and understood. There are several ways to interpret this claim. Some scholars have regarded “having number” as the necessary condition for the mere apprehension of an object. If something is not countable and hence distinguishable from other things, it can’t be recognized as a separate entity at all (Nussbaum 1979; Kirk, Raven and Schofield 1983, 327). The epistemological vocabulary which Philolaus uses (noein and gignôskein), however, more typically refers to understanding and knowledge than to simple apprehension of an object (Huffman 1993, 116–118). Several fragments make appeals to sense experience without mentioning the concept of number (e.g. Fr. 2), so that it would appear that Philolaus thinks that we can initially apprehend objects through our senses but that we only come to have true knowledge or understanding of them by grasping their number. Fragment 13 makes a clear distinction between sense perception, which humans and animals share, and understanding, which is limited to humans. Animals can apprehend objects in the world just as humans do, but they do not understand them because they cannot grasp the numbers which govern them, as humans can. Such an interpretation is supported by Fragment 5: