My framing of postmodern thought is here: Why is post-modernism so often equated to Relativism, are there any responses in postmodern philosophy that challenges this?
TLDR: Postmodern thinkers attack the idea of a transcendental reality with universal truths, which should be understood not as an attack on the possibility of knowing things, but as a call to return to discourse to find them and pursuasion as the method to recruit others to those you've found, in alignment with scientific acceptance that all knowledge is tentative and relational and subject to future revision.
And this answer is my summary of dialectic thought:
Relation of dialectics, as of Hegel and Marx, toward Enlightenment liberalism
TLDR: Hegel & Marx offer a communitarian critique of a kind of 'transcendental individualism' at the basis of Enlightenment thinking and it's political expression in liberal democracies.
I see there as being a deep source of division about what reality is like founded in whether people are Mathematical Platonists or not. If people are, then physics can be about coming to know 'the mind of god', albeit a Deistic one. It means there can be one fundamental reality or set of rules for becoming, which all people in all places can come to know. For me the assumptions that lead to that picture are fundamentally monotheistic, and idealism-driven, even though most advocates are unaware of this. It tends to fit with philosophy modelled on maths anx logic, rather than as cultural critique.
There is an alternative. You can be an ontological relativist, if you hold that the apparent universals, say of mathematics, derive from intersubjectivity. That is, we have a peer-to-peer reality, as modelled by Indra's Net - which notably comes from non-monotheistic culture. I see numberlines as derived from translational symmetry, and mathematical operations as abstractions of other symmetry operations.
Though 'postmodern neo-Marxism' is an obvious canard, I would say we can understand a continuity between dialectic modes to find truth and Postmodern thinkers, as calling for attention to dialogue and discourse, over declaration of supposed universal truths implicitly founded in a metanarrative you are not 'allowed' to dissent from - that would be 'irrational', or condemned in some otherway usually enforced by a group with a monopoly on force.
The idea of Epistemic Justice is I think an interesting example of how Postmodern analysis is not simply absolute cultural relativism: Need help with this paper on epistemic justice Art, literature, philosophy, emerge within discourses within communities, and frame the units of concern and the dynamics between them in local terms, to address local events.
It is not about saying the Taliban ending education of women is fine because that's the local discourse, because we know Malala Yusufzi and many others are in that discourse, that community, and disagree. But instead of saying, we in the West have the correct reality and in it ending female education is evil; we should be entering into discourse, to pursuade the community as a whole. So, that might mean framing things in terms of Islamic judicial schools. It might also mean looking at why social change in the Islamic world like the Arab Spring or Iranian Revolution has led to hostility to change and Wahabi conservatism, and how mechanisms for positive social change can become more deeply rooted in the discourse - like by not saying time to become secular atheists because that's the only way to be.
The internet is a peer-to-peer network. Yet, we feel like we have 'one internet'. Prioritising discourse and pursuasion, doesn't mean no explanatory account or social system can be evaluated as more effective in it's own terms. But it does mean looking to the whole system of identity of a community, eg the metarrative, as well as engaging with the current narrative. We might compare metanarratives to site architecture; like say the set of modes to interact on Stack Exchange tend to lead to more productive discussions than the set that constitute Facebook; and that differences is set on top of a great deal of shared structure. We don't need a single set of ways to interact derived from universal principles; but a system of recruitment to systems of interaction that work. It's interesting to look at the Replication Crisis in psychology, in relation to how using mainly small numbers of participants among university students with a lot in common, has led to over-universalising about results and hidden how much we vary.
I would look to Durkheim, on how enacting attitudes towards truths held to be beyond (immediate) questioning, binds together groups with social-contracts between those that share the benefits of adhering to the group's values, and excludes those who don't share the values. We can relate group-narratives and their amendment through discourse like that.
So dialectic and Postmodern thought both draw attention to discourse away from transcendental truths embedded in an implicit metanarrative which smuggles in monotheistic assumptions; but the former seeks a developing metanarrative that is totalising, while the latter rejects the need to reconcile and integrate everyone into one structure of thought.
