Complex sentence: 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".
Split into simpler sentences: 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".