G. E. M. Anscombe, 'Modern Moral Philosophy', Philosophy 33, No. 124 (January 1958)
The uselessness of it. We need to start again from Aristotle.
P. Foot, 'Morality as a System of Hypothetical Imperatives', The Philosophical Review 81, No. 3 (July 1972) 305-316
Kant is wrong: morality cannot be a system of categorical imperatives.
W. V. O. Quine, 'Two Dogmas of Empiricism', Philosophical Review 60 (1951): 20-43
Debunking the analytic/synthetic distinction and arguing for the hypothetical nature of logic.