Attributions of relativism to Oakeshott are twofold:
The first, and the more common attribution, is from the general perspective of viewing Oakeshott as a postmodern relativist. The second, more technical aspect and less familiar attribution, involves the assumption that Oakeshott was a coherentist.
I examine the second view first. On this assumption it is standard to present Oakeshott with the following problem. It is empirically and conceptually possible that there are any number of ethical, political, and social beliefs and activities which form equally coherent systems, with ex hypothesi no decidability on grounds of coherence between them. And this is relativism (or one recognisable form of it).
Coherentism can inform both a theory of what we are justified in believing and a theory of truth. Indeed the two can be, and usually are, linked. We are justified in believing that X is the case if and only if:
(a) the belief that X is the case is consistent with all other beliefs in our system of beliefs; moreover and more strongly;
(b) those beliefs are mutually entailing; and
(c) the system of beliefs exhibits overall simplicity and is relevantly comprehensive.
The real work is done by condition (b), since (b) subsumes (a); and (c) is common to virtually all theories of justification. Then we can go from justification to truth by holding that truth just is the property of belonging to such a system of beliefs or worldview.
A standard problem with coherence as justification is that there seems no reason to accept that there is a single fully coherent and comprehensive system of beliefs or world view from the perspective of a given subject – individual mind or a collectivity of minds – at a given time. A problem about truth and coherence is that it fails to do justice to an intuition most of us have about truth – namely that conditions (a), (b), and (c) might all be met, and our belief that X is the case still be false.
There are a number of discriminations to be made. Oakeshott might be expected to reject the idea of a single fully coherent and comprehensive system of beliefs or worldview from the perspective of a given subject – individual mind or collectivity of minds – at a given time. This might appear to follow from the possibility, indeed the fact, of different modes of experience – or, later, conversational ‘voices’ – which are incommensurable. Coherence is to be indexed to a particular mode or voice. Since, for example, science and history are answering modally distinct sorts of questions, there need be no mutual entailment between our answers to scientific questions and our answers to historical questions.
Still the problems about coherence, either for justification or truth, are simply replicated at the modal level. Take science: there seems no reason to accept that there is a single fully coherent and comprehensive system of scientific beliefs or worldview from the perspective of a given subject – individual mind or collectivity of minds – at a given time.
So it matters whether Oakeshott was a coherentist, because (even when we have made these discriminations) he cannot avoid the problems of coherentism about justification or truth. He cannot charge us with his favourite criticism: ignoratio elenchi.
Two points are relevant to the issue of Oakeshott’s coherentism. The first is Terry Nardin’s perfectly fair point that Oakeshott’s account of the nature of coherence is so indeterminate that ‘the idea of coherence necessarily functions as a metaphor, not a technical concept’.  This is not quite decisive, however. Oakeshott might be an inadequate explicit theorist of coherence but still, implicitly, employ a specific notion of it. This leads to the second point. If we consider how Oakeshott conceives, in his famous phrase, ‘the activity of being an historian’, we see a non-coherentist account of justification and truth at work.
Now to the first view: Oakeshott as postmodern relativist. The most famous identification of Oakeshott with relativism came from Rorty in his co-option of Oakeshott’s metaphor of “conversation” in the service of his radical relativism. 
If we see knowing not as having an essence, to be described by scientists or philosophers, but rather as a right, by current standards, to believe, then we are well on the way to seeing conversation as the ultimate context within which knowledge is to be understood. Our focus shifts from the relation between human beings and the objects of their inquiry to the relation between alternative standards of justification . . . 
Rorty’s premature and notorious “death of epistemology” pronouncement is extremely puzzling. Rorty’s target was twofold: a correspondence theory of truth and foundationalist justification. Yet this was no longer part of the philosophical landscape. Ramsey had long since proposed a reliabilist theory of knowledge.  Quine had already challenged analycity ; Sellars “the Myth of the Given”  and Goldman  had presented a second generation formulation of reliabilism followed by David Armstrong’s version  culminating in Nozick’s reliabilism , which was very definitely in the air in the late seventies.
Podoksik  has made a compelling case for the view of Oakeshott as a defender of modernism rather than proto-postmodern relativist. Podoksik’s central task is to identify Oakeshott as a defender of modernity. He thus seeks to shift our perspective on the familiar views of Oakeshott as conservative anti-modernist or as proto-postmodernist. Podoksik does not claim that these views are simply false but that they are misleading unless we appreciate the inherent fluidity of these interpretive categories (Michael Freeden’s “ideological morphology”).
For Oakeshott the mark of the modern consciousness is the emergence of a plurality of distinct spheres of knowledge – poetry, science and history (inter alia). This plurality, insists Podoksik, should not lead us to derive postmodern relativistic conclusions – each of these domains are constitutive of their own criteria of objectivity and standards appropriate to their own subject matter. This sounds pretty much like postmodern relativism – the precise contrast with postmodernism is not as clear as Podoksik’s modernity thesis requires. A marked feature of Podoksik’s discussion is the substantial amount of time he devotes to the place of science in Oakeshott’s thought. Typically, commentators talk up Oakeshott’s anti-naturalist credentials almost as a matter of professional pride. Podoksik rightly views this emphasis as one-dimensional: Oakeshott’s adminadversions against scientism should be counterbalanced by his intention to maintain the integrity of science, rescuing science from misplaced scepticism and the relativism that is corrosive of one of modernity’s great achievements. Podoksik has made an excellent effort to examine the scientific influences upon Oakeshott’s sparse writings on the topic. His conclusion is surprising: that Oakeshott has more in common with the scientific positivism of Mach and Poincaré than with the antinaturalists and relativists he is so often allied with.
 The Philosophy of Michael Oakeshott, Penn State, 2001, p. 22; O’Sullivan, L. (2003) Oakeshott on History, Exeter: Imprint Academic, p. 88.
 Philosophy and the Mirror of Nature, Blackwell: Oxford 1980, rep 1994, pp. 264, 318, 389; Rorty R. (1997) Objectivity, Relativism and Truth (Cambridge: Cambridge University Press. p. 197.
 Philosophy and the Mirror of Nature, Blackwell: Oxford i980, rep. 1994, p. 389
 Ramsey, F. P. (1929) “Knowledge”, rep. in Philosophical Papers (1990), ed. D. H. Mellor, Cambridge: Cambridge University Press.
 W.V. Quine, “Two Dogmas of Empiricism”, From a Logical Point of View (Cambridge MA: Harvard University Press. 1953), p. 37.
 Sellars, W. (1956) “The Myth of the Given: Three Lectures on Empiricism and the Philosophy of Mind.” rep. in Empiricism and the Philosophy of Mind, (Cambridge, MA: Harvard University Press, 1997).
 “A Causal Theory of Knowing” Journal of Philosophy, v. 64 (1967)
 Belief, Truth, and Knowledge, Cambridge, 1973, pp. 162-75
 Philosophical Explanations, Harvard (1981).
 Podoksik, E. (2003) In Defence of Modernity: Vision and philosophy in Michael Oakeshott, Exeter: Imprint Academic
 This piece is an excerpt from my “Constructivism and Relativism in Oakeshott“.