(a) What are the main arguments put forward by Moore in his paper "A Defence of Common Sense" to prove that there are possible…

(a) Moore's defence of common sense

In "A Defence of Common Sense" (1925) Moore lists truisms that he knows with certainty: that there now exists a living human body which is his body, that the earth has existed for many years, that it has been near other bodies, and that other human beings have had experiences. His arguments are four.

First, each truism is something he knows to be true, and he is more certain of it than of the premises of any argument against it.

Second, sceptical and idealist philosophers who deny them take the same truths for granted when they speak, write and address readers; their denial is therefore self-defeating.

Third, one can understand and know a proposition to be true without knowing its correct philosophical analysis. Disputes over analysis do not touch the certainty.

Fourth, in "Proof of an External World" (1939) he shows his hands, concludes "here are two hands", and so deduces that external things exist. The premises are better known than the sceptic's doubts.

Evaluation: the argument works as a shift of burden, since a sceptical premise must be more credible than a plain perceptual claim. It does not, however, answer the sceptic who says that knowledge of the premise is exactly what is in doubt, so it is open to the charge of begging the question (Stroud). Wittgenstein (On Certainty) held that "I know" is misused here: such propositions are hinges of inquiry, not items of knowledge. Moore's argument does show that the sceptic's premises are no more secure than common sense, but it falls short of refuting the sceptic.

(b) Strawson on basic particulars

In Individuals (1959) Strawson calls a particular basic if identifying reference to other kinds of particular depends on it, while its own identification does not depend on them. Events and processes depend on the bodies and persons to which they belong.

Material bodies are basic because they are public, enduring, spatially extended and re-identifiable. Re-identifying particulars through time requires a single unified spatio-temporal framework, and bodies furnish its fixed points. The "no-space" auditory world argument shows that sounds alone cannot supply such a framework.

Persons are basic because the concept of a person is logically primitive. It is the concept of an entity to which both M-predicates (corporeal, such as "weighs 70 kg") and P-predicates (states of consciousness, such as "is in pain") apply, in the same sense for oneself and others. It is not derivable from a Cartesian ego or a body to which a mind is added.

Criticism: the argument is a descriptive inquiry into our conceptual scheme and does not show that no other scheme could exist. Cartesians reject the primitiveness of the person. The status of persons as basic yet also a special kind of body is open to question, and Quine proposed alternative ontologies.

(c) Quine's empiricism without the dogmas

In "Two Dogmas of Empiricism" (1951) Quine rejects two dogmas: the analytic-synthetic distinction, and reductionism, the belief that each meaningful statement is equivalent to a construct out of immediate experience.

On the first, analyticity cannot be defined without circularity. Definition, synonymy, interchangeability salva veritate and semantical rules all presuppose the notion they are meant to explain ("No bachelor is married").

On the second, statements face experience not singly but as a corporate body (Duhem-Quine holism). Our knowledge is a web whose edges meet experience, and any statement may be revised if the rest is adjusted, even logic.

The resulting empiricism is holistic and pragmatic. Physical objects are posits, like Homer's gods, justified by their usefulness in organising experience.

Criticism: Grice and Strawson (1956) argued that the distinction survives in ordinary practice. Carnap's framework answer and Putnam's later point suggest that Quine's holism does not erase differences in revisability. Total holism risks making confirmation untestable.