Full Idea
Quine is suggesting that philosophy should abandon the attempt to provide a foundation for knowledge, or otherwise justify it, and should instead give an account of how knowledge is acquired.
Gist of Idea
We should abandon a search for justification or foundations, and focus on how knowledge is acquired
Source
report of Willard Quine (Epistemology Naturalized [1968]) by Donald Davidson - Epistemology Externalized p.193
Book Reference
Davidson,Donald: 'Subjective, Intersubjective, Objective' [OUP 2001], p.193
A Reaction
If you are going to explain how 'knowledge' is acquired, you'd better know what knowledge is. My suspicion is that Quine would be quite happy (in the pragmatist tradition) to just focus on belief, and forget about knowledge entirely.