Coherentism (including ethical coherentism)
Coherentism is a term used chiefly in epistemology, meaning the position that a belief is justified by its coherence with other beliefs that we already hold. For coherentists, there is not one set of infallible or foundational truths that we can appeal to justify all our other beliefs (such as Descartes cogito, "I think therefore I exist"), but rather just an intersecting relationship with all the other beliefs we hold. The analogy of a jigsaw puzzle can be used to illustrate coherentism: we believe that a certain piece in a jigsaw puzzle is in the right place only because of its relationship to the other pieces, that together create a coherent picture.
Ethical coherentism is coherentism of this kind used specifically to justify moral beliefs. For an ethical coherentist, a moral belief is justified only by its relationship to other moral beliefs.
In Middle Way philosophy, coherentism is identified as a key type of negative metaphysical assumption common in modern moral and other philosophical discussion. Coherentism is found, for example, in much modern discussion of ethics in analytic philosophy, because of the underlying assumption made there that the only possible justification of ethics is a conventional one. In analytic ethics, the basis of judgement is one of consistency with our "everyday moral intuitions". If moral beliefs are justified only because they are consistent with other moral beliefs that we already hold, or because they are consistent with moral beliefs held in our society, the outcome is likely to be very conservative. Because of its reliance on coherentism, analytic ethics rule out in advance all possible moral challenges to a conventional position.
The underlying weakness of coherentism is that any judgement appealing only to coherence may be coherent only with further false beliefs. As a mode of justification, coherentism also ignores the tendency of the human mind to create coherence out of whatever experiences it encounters, in the process failing to address conditions that do not fit the coherent model being imposed on things. Coherentism takes insufficient account of human ignorance, for coherence is not equivalent to truth. This epistemological point about coherentism in general applies both to ethical coherentism and to other applications of coherentism as a basis of judgement.
It nevertheless must be conceded that coherence is one important element of objectivity. If a set of beliefs is incoherent, this is one possible reason for justifiably rejecting them as lacking objectivity. Coherence is necessary for objectivity, but it is not sufficient. Objectivity requires a balancing of the need for coherence with negative foundationalism .
In the analysis of Western moral philosophies found in 'A Buddhist theory of moral objectivity', pointing out the limitations of coherentism provides a basic epistemological justification for the rejection of both scientistic and existentialist forms of nihilism: in other words, we cannot reject the possibility of objectivity in ethics either by appealing to the supposed objectivity of facts by contrast, or by arguing that all judgements about either facts or values are merely individual. Both of these approaches involve an implicit assumption that the coherence of social or of individual moral beliefs is sufficient for their justification in practice.
Further discussion
Ethical coherentism as a feature of nihilism (from thesis)
Analytic philosophy (from thesis)
Existentialist philosophy (from thesis)