Let us begin by a thesis that:
Concept of “nature” as provided by natural sciences is the hindrance in the way of any reconciliation between “nature” and “reason”.
Now there are, many possible ways out, but first a “caution”:
“The reconciliation is to be done without blurring distinction between “reason” and “nature”. In another words there is a distinction which should not be blurred but there is no legetimation for turning that distinction into a dichotomy.
Now here is one possible way out (on this occasion only from the perspective of “nature’ though similar should be done from the side of “reason”):
1) Reconceptualise the concept of “nature” as dealt within natural science.
1a) But the above is ambiguous: It can either mean re-conceptualizing the concept of “nature” as it is used in sciences. It would be argued that unless we arrive at a new conception of science which is qualitatively different form current physicalist reductionist conception of science we cannot effect any reconciliation between nature and reason. Marcuse and his disciples argued for such a position. Habermas is vehemently opposed to such ideas. He sees in them germs of anti modernism.
1b) or it can mean re-conceptualizing the concept of nature as a whole in such a way that the concept of nature as found in sciences would be part of an overall conception of nature (an abstraction albeit a legitimate one) and would not be regarded as equal to nature as such. Then we would have an ample room for experimenting with our idea of reconciliation between nature and reason without abandoning current notions of what science is apart from denying reductionist philosophies based on an appeal to sciences.
2) Obviously Habermas would favour (1b).