The Muses, therefore, were both the embodiments and sponsors of performed metrical speech: "mousike" (whence the English term "music") was just "one of the arts of the Muses". Others included Science, Geography, Mathematics, Philosophy, and especially Art, Drama, and inspiration. In the archaic period, before the widespread availability of books (scrolls), this included nearly all of learning. The first Greek book on astronomy, by Thales, took the form of dactylic hexameters, as did many works of pre-Socratic philosophy. Both Plato and the Pythagoreans explicitly included philosophy as a sub-species of "mousike". The "Histories" of Herodotus, whose primary medium of delivery was public recitation, were divided by Alexandrian editors into nine books, named after the nine Muses.