Two views of philosophy

The following is David Lewis's characterization of philosophy:

One comes to philosophy already endowed with a stock of opinions. It is not the business of philosophy either to undermine or to justify these preexisting opinions, to any great extent, but only to try to discover ways of expanding them into an orderly system. [...] There is some give-and-take, but not too much: some of us sometimes change our minds on some points of common opinion, if they conflict irremediably with a doctrine that commands our belief by its systematic beauty and its agreement with more important common opinions. (Counterfactuals, p.88)

I am not sure what to make of it. On the one hand, this goes against my conviction that philosophy is by nature self-critical; on the other hand, I have to admit that what Lewis says is true of many philosophers, including himself.

Compare this with the following passage by Foucault:

After all, what would be the value of the passion for knowledge if it resulted only in a certain amount of knowledgeableness and not, in one way or another and to the extent possible, in the knower's straying afield of himself? There are times in life when the question of knowing if one can think differently than one thinks, and perceive differently than one sees, is absolutely necessary if one is to go on looking and reflecting at all. [...] what is philosophy today --- philosophical activity, I mean --- if it is not the critical work that thought brings to bear on itself? In what does it consist, if not the endeavor to know how and to what extent it might be possible to think differently, instead of legitimating what is already known? (The Use of Pleasure, p.8)

I find myself agreeing with Foucault, though I am not sure to what extent philosophical reflection can change one's fundamental world view. Yes, "to the extent possible", but what is that extent? So, this is inspirational, but I am not sure how true it is of actual philosophers.

I am torn between these two views of philosophy.