A very common objection to the philosophical enterprise among contemporary critics is what I will tentatively call the Objection from Progress. The objection is that if philosophy were truly a science, then its history would at least partially resemble the history of other sciences, meaning that it would begin crudely as men were first exploring its existence and implications, and with the passage of time it would develop through breakthrough, discovery, paradigm shifts, etc. Now philosophy's history does not look like this at all, therefore it is not a science or even a source of meaningful knowledge.
But is this true? Before the revolution that is modern philosophy came about, beginning officially with Descartes, many philosophers did see philosophical history in a way similar to the way men view sciences like physics today.
The first philosopher to give a comprehensive history of the development of philosophy was Aristotle, who considered himself as progressing beyond what came before. His history of philosophy began with Thales, who posited water as the ultimate principle of all things. Then Anaximenes and Diogenes posited air as the more fundamental principle. Hippasus and Heraclitus thought fire to be the cause of all things. Following these, Empedocles said that all three were principles of being, along with earth, and that it is through the unification and separation of these four elements that the things of our world come to be. After Empedocles come the atomists Democritus and Leucippus. They thought that the world was composed of atoms, or indivisible bodies, and empty space (so as not to make the world one continuous whole being) and that these atoms were arranged differently according to shape and position, The last school before Plato is that of the Pythagoreans who offered number as the source of all things. There is a relation between the teachings of the Pythagoreans and Plato inasmuch as number approaches formal causality, which Plato was the first to fully articulate.
This is a very rough introduction to the history of western philosophy given by Aristotle. Putting aside monists like Parmenides who denied coming-to-be altogether, there is one theme that runs through this crude, embryonic, underdeveloped beginning to philosophical speculation: until Plato it is all materialist.