I think this article does a great job of delineating the Modern/Postmodern divide. As I see it, though, Postmoderns have (ironically, of course) joined with Moderns in equating 'reason' with 'rationality'. The two are not the same.

To 'reason' is to construction of a chain of logically coherent statements. Reason can be used to defend a premise or arrive a conclusion from a premise. That premise can be a belief (sacral or secular) or some other non-rational abstraction (such as a feeling or an intuition).

To refer to any reality outside of material existence is extra-rational. To be strictly rational a chain of reasoning must be wholly contained--its starting point and its ending point--within material existence. Science is an example of such rationality.

Such rationality does not necessarily generate universality: humans have the capacity to know (for our individuated selves) of extra-rational realities that 'trump' even the most obvious material realities. Using theology or ideology to judge the veracity of scientific findings is one example of such mental processes. Denying the physical reality of global warming comes to mind. Various religionists engage in such mental activities. Lenin made it an explicit tenet of the Bolshevik Party that "theories” of history and even science could only be valid if they "conformed with" Marxist-Leninist ideology. Fascists subvert science to ideology, too.

Since material reality is the only reality that can be a shared experience within material existence, however, the products of such strictly rational mental processes are as close as human beings can come to the commonality necessary for shared responses to realities affecting the material well-being of any group of human beings — to include the group of all human beings— such as global warming. Beyond that, I have made a case for observation within material existence as providing the only possible non-coercive ethic for governing governance of societies.