When a new epoch opens up in the history of philosophical thought, it often transpires that the very thinkers who first helped to encourage and prepare the way for this development themselves fall into almost immediate oblivion. There are therefore a host of figures who were once considered significant participants in the philosophical debates of the past and proved effective and tenacious opponents of now celebrated philosophers, but who are now only familiar to us from the assessment they have received in the works of the philosophers in question. One purpose of historical research in the philosophical field must be to reveal a proper and fuller picture of the thought of such figures behind the faded image of them, which is generally communicated to us by the great and now-established names of subsequent philosophy. Only then shall we find ourselves in position, with independent judgement of our own, to evaluate the real significance of such figures for the emergence of a genuinely new line of philosophical thought. As far as classical Greek philosophy is concerned, there are particular difficulties facing this task insofar as the only texts now surviving from the time of the original manuscript's creation are those that were judged to be the most significant at the time.