@kennethamy,
Well, dear Kennethamy, first, I emphasized in the first place that "tracing back to its origin"is only "one way" to determine the purpose-namely, there could be other methods; second, I did not claim that "tracing-to-origin" strategy is a panacea in determining purpose(s) of
every subject. This strategy may not even be applicable to the examination of the purpose(s) of philosophy. But when you get back to its origin, it surely gives you some insight as to, at least, why philosophy appeard-that is to say, philosophy came into being out of certain purposes initially; and the purpose of it was adjusting what was falsified or misled.
According to Aristotle, everything's existence can be accounted for by a purpose. Althought this theory seems a little bit out-dated, it nevertheless shed some light upon the topic being discussed here.
Be that as it may, a subject may well have different purposes during different eras/periods. But, for me, philosophy serves as a tool whereby we seek truth.
Waitting for your response.