http://plato.stanford.edu/entries/naturalism/
The term ‘naturalism’ has no very precise meaning in contemporary philosophy. Its current usage derives from debates in America in the first half of the last century. The self-proclaimed ‘naturalists’ from that period included John Dewey, Ernest Nagel, Sidney Hook and Roy Wood Sellars. These philosophers aimed to ally philosophy more closely with science. They urged that reality is exhausted by nature, containing nothing ‘supernatural’, and that the scientific method should be used to investigate all areas of reality, including the ‘human spirit’ (Krikorian 1944, Kim 2003).
So understood, ‘naturalism’ is not a particularly informative term as applied to contemporary philosophers. The great majority of contemporary philosophers would happily accept naturalism as just characterized—that is, they would both reject ‘supernatural’ entities, and allow that science is a possible route (if not necessarily the only one) to important truths about the ‘human spirit’.
Even so, this entry will not aim to pin down any more informative definition of ‘naturalism’. It would be fruitless to try to adjudicate some official way of understanding the term. Different contemporary philosophers interpret ‘naturalism’ differently. This disagreement about usage is no accident. For better or worse, ‘naturalism’ is widely viewed as a positive term in philosophical circles—few active philosophers nowadays are happy to announce themselves as ‘non-naturalists’.[1] This inevitably leads to a divergence in understanding the requirements of ‘naturalism’. Those philosophers with relatively weak naturalist commitments are inclined to understand ‘naturalism’ in a unrestrictive way, in order not to disqualify themselves as ‘naturalists’, while those who uphold stronger naturalist doctrines are happy to set the bar for ‘naturalism’ higher.[2]
Right about this.
Some extreme naturalists deny that a priori conceptual knowledge is so much as possible (Devitt
2005). They take Quine’s case against an analytic-synthetic distinction to show that all claims are
answerable to empirical data and so not purely analytic. This is not the place to assess Quine’s
arguments, but it seems unlikely that they can establish so strong a conclusion. (Suppose that a
certain group agrees, say, that they are going to use ‘Eve’ to refer to the most recent common
matrilineal ancestor of all extant humans. Then surely that know a priori that, given general
evolutionary assumptions, all contemporary humans are descended from Eve.)
Not quite. It is quite possible that there is no such most recent common matrilineal ancestor. One wud need (empirical) data to know that.