On Nature
Empedocles is considered the last Greek philosopher to write in verse. There is a debate about whether the surviving fragments of his teaching should be attributed to two separate poems, "Purifications" and "On Nature", with different subject matter, or whether they may all derive from one poem with two titles, or whether one title refers to part of the whole poem. Some scholars argue that the title "Purifications" refers to the first part of a larger work called (as a whole) "On Nature". There is also a debate about which fragments should be attributed to each of the poems, if there are two poems, or if part of it is called "Purifications"; because ancient writers rarely mentioned which poem they were quoting.