What Quine is famous for, among other things is his advocacy that an thorough understanding of language means that there is no real demarcation between philosophy and science like the logical positivists tried to maintain. So, while Mauro is right in delineating "foundationalist" philosophers (particularly Descartes and his confidence in introspection as "first principles"), I think it's fair to say that in a more immediate sense, Quine was responding to the logical empiricists (SEP) and the logical positivists who are often referred to as the Berlin and Vienna circles. These philosophers were openly hostile to metaphysics and tried to show (without success) it could be eliminated. Thus, for the LPs, philosophy was nothing more than linguistic analysis.
Quine also believed in science, mathematics, and logic (the natural and formal sciences), however, he attacked some of the philosophical foundations that men such as Rudolf Carnap took as a starting point in their reasoning, in particular the analytic-synthetic divide that proposed by Kant and used heavily by the German Idealists followed later by the Germans who laid the foundation of modern analytical philosophy (according to Dummett). In his Two Dogmas of Empiricism, Quine attempts to show that there is no clear distinction between strictly analytical propositions which are true a priori, and synthetic truths which are real-world a posteriori. By doing so, he manages to soften up the notion that some truth belongs solely to the introspective powers of reason (read as philosophy) and others soley to sensory experience (read as science). If there's no strict border between truths of logic and truths of senses and observation, then philosophy and the science must in a manner exist as a continuum also with theories that co-mingle propositions of each sort. Quine is also known for his “Epistemology Naturalized” and in fact, he emphasizes the wholistic nature of thought:
On Quine's account, attempts to pursue the traditional project of finding the meanings and truths of science philosophically have failed on their own terms and failed to offer any advantage over the more direct methods of psychology. Quine rejects the analytic-synthetic distinction and emphasizes the holistic nature of our beliefs. Since traditional philosophic analysis of knowledge fails, those wishing to study knowledge ought to employ natural scientific methods. Scientific study of knowledge differs from philosophic study by focusing on how humans acquire knowledge rather than speculative analysis of knowledge.1 According to Quine, this appeal to science to ground the project of studying knowledge, which itself underlies science, should not be dismissed for its circularity since it is the best option available after ruling out traditional philosophic methods for their more serious flaws.
Contemporary philosophers have elaborated and commented on Quine's views extensively. Today, there are a variety of criticisms and plenty of lavish support for his ideas, and those folks, according the SEPs article Naturalism in Epistemology might be characterized as "moderate naturalism" which appeals to two criteria:
Moderate Naturalism
(A) All epistemic warrant or justification is a function of the psychological (perhaps computational) processes that produce or preserve belief.
(B) The epistemological enterprise needs appropriate help from science, especially the science of the mind. (Goldman 1999a: 26)
(Oddly to me) there is still some resistance to some of these statements for a variety of reasons (that you'll hear on this forum). In the extreme, not only does philosophy and science essentially overlap because logic and language reduce to psychology partially, but some philosophers take this relationship as license to practice science themselves to make assertions about philosophical principles. The sciences grew out of natural philosophy, and every science (formal or natural) has a healthy philosophy-of (philosophy of physics, chemistry, biology, etc.). But research, say in the psychology relevant to bias, may have impact on the philosophy of language or logic. According to An Introduction to Metaphilosophy:
[Experimental philosophy] seeks to replace or supplement traditional [philosophical] analysis with empirical, experimental data, specifically collected for the purposes of illuminating some philosophical question.
This, of course, has always been the case, but the appellation "experimental" is a relatively newer self-identification of philosophers. According to the SEP's Experimental Philosophy:
Experimental philosophy is an interdisciplinary approach that brings together ideas from what had previously been regarded as distinct fields. Specifically, research in experimental philosophy brings together two key elements:
- the kinds of questions and theoretical frameworks traditionally associated with philosophy;
- the kinds of experimental methods traditionally associated with psychology and cognitive science.
There are many philosophers (a very broad term indeed) who still believe there is some strict wall between philosophical and scientific practice based on topic or methodology, but I suspect on the whole most philosophers of metaphysics, language, and science don't believe there is a strict division like the logical positivists maintained, and in this sense Quine's view stand strong in the face of the failure of the logical positivist programme.
In contemporary philosophy, foundationalism has been defended by Edmund Husserl,[13] Bertrand Russell[14] and John McDowell.[15][16]" (Wikipedia)
– Starckman Feb 12 '23 at 09:05