Ronald Dworkin, answered from the texts and cited to the page.
Value-claims hang together. Ethics (how to live), morality (what we owe to others), political philosophy (how the state should be organized), law (how courts should decide hard cases) are not separate inquiries with potentially incompatible answers; they are one inquiry whose claims must cohere. This is the hedgehog thesis — taking up Archilochus's distinction between the fox who knows many things and the hedgehog who knows one big thing — and the one big thing is the unity of value.
Two great values, dignity (the requirement that each person take her own life seriously) and equal concern (the requirement that governments treat each citizen's life as equally important), anchor the rest. The metaethical view that makes this possible is interpretive realism: value- claims are objectively true or false, but their truth is not a matter of correspondence to a separate moral realm. External skepticism — the view that there is no value- reality so value-claims cannot be true — misunderstands what value-claims do.1
We do not make value-claims by describing a special domain of moral facts; we participate in interpretive practice, and our claims succeed or fail depending on the quality of the interpretation. J. L. Mackie's error theory, Bernard Williams's truth-in-ethics skepticism, Simon Blackburn's expressivism, Gilbert Harman's relativism all fail to see that the question 'is torture really wrong?' is itself a moral question, not a metaethical one. To ask it well requires moral argument, not metaethical reduction.234
In Chapter 6 I describe a theory of moral knowledge, responsibility, and conflict, and in Chapter 8 a theory of moral truth. These theories are drawn from within morality— they are themselves moral judgments. That is what independence means in moral philosophy. It is a natural and entirely familiar view: it is how we think. There is no noncircular argument against it.Justice for Hedgehogs, pp. 10–11
Value is one big thing. The truth about living well and being good and what is wonderful is not only coherent but mutually supporting: what we think about any one of these must stand up, eventually, to any argument we find compelling about the rest.Justice for Hedgehogs, pp. 21–22
Their arguments and examples show that they have our private lives rather than our politics in mind, however. I think them wrong about private lives: I argue in Chapter 9 that our dignity requires us to recognize that whether we live well is not just a matter of whether we think we do.Justice for Hedgehogs, pp. 8–9
There would be no reason to think that these brute values are always nicely knit together in the mutually accommodating way that hedgehogs imagine.Justice for Hedgehogs, pp. 11–12
The hedgehog thesis is the late-Dworkin metaethical synthesis and the most ambitious philosophical statement of his career. Justice for Hedgehogs (2011) was widely reviewed and widely contested; the reception ranged from sympathetic engagement (Joshua Cohen's Boston Review symposium, Scott Hershovitz's essay) to sharp critique (T. M. Scanlon, Jeremy Waldron, F. M. Kamm in various venues). The interpretive metaethical position is genuinely unusual in the contemporary metaethics literature, which is largely structured around the realism/anti-realism axis where Dworkin's view does not sit comfortably. The value-pluralism tradition of Isaiah Berlin and Bernard Williams remains the principal liberal alternative to the unity-of-value thesis. The recent moral-realist tradition (Derek Parfit's On What Matters, David Enoch's Taking Morality Seriously) shares the anti-skepticism but rejects the interpretive component; the constructivist tradition (Korsgaard, Scanlon) shares the rejection of correspondence-realism but rejects the claim that ethics and morality have a unity. The hedgehog thesis is the most under-engaged of Dworkin's major positions; the field is still catching up to it.