Singularly final unifying theories are a – or indeed, the – holy grail. The most significant barrier to unifying theories is that we expect them to be domain-specific, narrow and effectively limited – i.e. epistemologically “controlled” or even “controllable”. That’s the core problem – unified and/or unifying theories are constitutively not limited. Further, I expect that as a consequence of the logical “shape” such a theory must take – the insights and consequences would likely flow out into many other areas of thought and analysis. Finding an analytical, complex systems skeleton-key in any one domain likely unlocks many other potentially unexpected doors.
I’ve been down this philosophical rabbit hole for a number of years. I’m not certain that unifying theories in neuroscience, for instance, are any more (or less) cognitively unpalatable than sociological, biological or – indeed – cosmological versions. They all share something in common, far beyond the challenge they represent to a narrative psychology that prefers (as much as the language it inhabits) to perceive and project a teleological closure upon facts that may reveal itself to be quite substantively fictional.