There is an entry at Britannica.com for Poststructuralism, the philosophy of the “social construction” of meaning that informs many of today’s movements in art:

…It held that language is not a transparent medium that connects one directly with a “truth” or “reality” outside it but rather a structure or code, whose parts derive their meaning from their contrast with one another and not from any connection with an outside world.

This is of course an over-simplification, as these things usually are; nevertheless, for this discussion it will do well enough.

For poststructuralists, the project of art is largely a project of liberation from authoritarian meanings constructed by elites.  It is a recognition of the artificiality of such meanings, and therefore of their illegitimate claim to “objective reality.”  On the contrary, meaning is shown to be emergent in the structure of language and culture, and therefore, participatory in its essence.  Meaning is a personal and social construct, to be built with others in a participatory fashion.

There is an aspect of the underlying assertion about language that conforms well with the latest insights in science and mathematics; but there is another aspect of this assertion that is entirely inconsistent.  That is the distinction I want to take up here.

The conforming aspect is that structure is connected to meaning, or rather, that meaning emerges from structure.

Philosophers of science have struggled for centuries to resolve a duality at the heart of science:  the schism between the subjective world of qualitative experience and the objective structural world of quantitative "facts."  This schism has slowed progress in fields as diverse as neuroscience, cognition, genetics, even physics itself.

But new insights are pointing to a powerful resolution of the paradox of how "nature lifeless" could result in "nature alive," as Whitehead put it. New insights into the phenomenon of life suggest that it is indeed a vastly complex kind of emergent structure, and that feeling and subjectivity arise from this structure.  There is no need to posit a transcendent world.

It is vital to understand that this does not “psychologise” meaning, explain it away as a structural trick or an artificial property of structure.  (I need hardly point out that such a trick would do nothing to resolve the ongoing mystery of meaning, but only push it off into yet another inaccessible spot.)

Rather it makes meaning an immanent trait of structure, a latent property to be articulated and amplified in structure.  It is in essence an a priori, to be participated in directly, but not to be explained in terms simpler than itself – for there are none.  Nonetheless it is emergent from structure, and shaped, amplified and conditioned by it.  

Hence language can indeed amplify and transform meaning, in the brain of the animal that experiences it.  In this sense it can indeed be “socially constructed.” 

But there is an aspect of the poststructuralists' analysis that does not conform to scientific understanding -- indeed, I argue is entirely inconsistent with it.  It is the assertion that language has no connection to any supposed “outside reality”.  This massive epistemological step was taken to get around the usual ontological quagmire:  what we mean by “reality,” what is meant by its “objective” status, who gets to determine this, what elite and arbitrary power do they have, and so on.  The poststructuralists want to dispense with all that.   Whether there may or may not be an “objective reality” beyond language is irrelevant.  For their purposes, “there is nothing outside the text,” in the words of Derrida.  This simplifies and clarifies things enormously.

But  there is a fundamental self-contradiction in the poststructuralists' effort.  Their attempt to deny objective reality is a perfect mirror of the positivists' denial of subjective reality before them.  In doing so each seeks to deny a metaphysical discussion that might unite the two. But such an effort leads to inexorable logical contradictions. 

For to deny the reality of a metaphysical realm is itself a metaphysical statement!

In the bargain the poststructuralists enter a fatally troublesome semiotic hall of mirrors.  As Eco pointed out, the thing about semiotics is that a sign can only be a sign if it signifies something.  The meaning of a thing has to originate in the structure of space in some way – in the structure of the real physical world. 

The scientific untenability of the post-structuralist epistemological position has been demonstrated in a variety of ways, including Sokal’s famously scandalous spoof.  For scientists, it is exceedingly difficult to say anything coherent and useful about the physical world when one posits that it is entirely a subjective creation, or at any rate that it must be treated as such.  

But such a quagmire results when one posits two distinct realms, the "physical" world and some other world of meaning, value, feeling, spirit, life -- precisely the divide that the new sciences demonstrate is no longer necessary.  The world is structural;  and it is meaningful.  This is a powerful insight.  And it does not require the poststructuralists' absurdist contortions.

There is now emerging a new way of looking at things that I will call "symmetric structuralism."   The term “symmetry” refers here to an isomorphic property between two structures, such that one has “symmetrical” (same-measure) aspects in relation to the other.  Importantly, these features will be simpler than either structure in total.  They will be, in essence, abstracted structural relationships.  But in each case they will nonetheless be real features of the "real" world, and "really" related to one another in the structural way in question.

Thus "abstraction" does not require some "unreal" realm; it simply exists as a class of structural relationship.

In this view, language is only one form of symmetrical structure, in a universe that is loaded with it.  Symmetry in this sense is very nearly identical to the notion of “information” – but it reminds us that information is always information about something, some real structure in space. That is, one construct (language, DNA, etc.) has a structure that is in some way isomorphic with respect to another.

This isomorphic characteristic can be exceedingly abstract.  For example, I happen to have my father’s blue eyes: that is a direct and visible symmetry, and not at all abstract.  But it is transmitted through genetic information that is exceedingly abstract relative to the actual characteristic of the eye itself.  It is, by definition, much simpler than the actual embedded phenomenon that it codes for. In fact there may be virtually no information about the appearance of the eye itself – only simple rules for expressing proteins that in fact will grow into the structure I recognise as being symmetrical to my father’s eyes.   The results may well be emergent and unpredictable.

None of this matters in nature.  The information – the symmetry – is retained, perhaps re-adapted in some way, and transformed.

The important point to grasp here is that language is simply another form of symmetry in nature -- more specifically, a coded symmetry.  And it is the failure to properly account for that fact – to posit some separate, unconnected realm of language and human meaning – that gets us into such a hall of mirrors.

This view of things (this model, or this symmetric structure!) can get us out again, and into the full-blooded world of structure -- and emergent meaning.

Further, this view of things carries profound implications for our art, our architecture, and our intelligent interaction with a threatened world. 

The deficiency of the poststructuralists is precisely that they can do nothing about the "real" world, because they deny the very basis on which we would know about this world and intelligently interact with it.  All we can do is construct shared meanings about our plight.  Meanwhile, we seem to have no responsibility for it, because we have no power to act.  We literally have no ability torespond.

Hence the necessary abandonment by the deconstructivists, and other related neo-modernists, of any project of betterment for humanity, save a better and richer experience of art.  At best, even that is "inter-subjective." 

The architect/artist cannot possibly make architecture that improves the quality of people's lives, because there is no agreement -- no possible agreement -- on what that might mean.  Such a "meaning" would merely represent the hegemony of one privileged elite viewpoint over others.  Who is to say, for example, that car exhaust is bad for people over time, or that a disordered environment is psychologically damaging? Such claims are merely the narratives of professional elites from medicine and psychology, imposing their own privileged constructions. 

Nor is there any hope of making architecture that is balanced and sustainable, like nature, or like the exquisitely-adapted patterns of old and venerable human settlements.    Rather, to achieve "sustainability," specialist engineers, part of the technocracy, might perhaps step in and provide some new apparatus that will form the basis for more architectural art.  They might, or they might not -- but we as artists must deconstruct that reality, and work with it.  We must accept this rigid technological reality, and hope for some miraculously sustainable gadgets within it.  We might imagine that such a thing is possible as part of some mythic futurist vision.

There is another problem with learning any lessons from the patterns of history. Since all is semiotics, structural lessons offered by history inevitably come with unacceptable political baggage, and therefore can offer no useful bits of DNA.  We must always start fresh, and relentlessly pursue novelty.  We may use bits of historic structure, but only as an ironic referent to be deconstructed.

This desperate poststructuralist architecture is perhaps an extreme view of things, and indeed many architects have claimed to disavow it;  but the fact remains that its fundamental epistemology is ingrained in global culture and global architecture in the late twentieth and early twenty-first centuries.  That is why, far from being an odd fringe movement, poststructuralism represents a logical final expression of the segregated Western view of structure and meaning, objectivity and subjectivity, or, as Whitehead put it, "nature lifeless" and "nature alive."

That is why I argue that poststructuralist art is not the flowering of a new paradigm, but the last expression of a dying one -- collapsing into inexorable self-contradiction. 

But a view of the world that follows on what I have called symmetric structuralism looks completely different.  Since all is structure -- including language -- we can use language to construct isomorphic models of the human condition, and models of various scenarios to extricate ourselves from whatever situation we find untenable.  We can construct "pattern languages" that assemble bits of structure in new ways.  

We can also now clearly recognise that any symmetry, any isomorphism, any code, deletes or ignores vast amounts of information.  Every physical construct is embedded in an infinitely complex context, and the symmetrical relation is precisely its extrication, its abstraction, from this embedded context.  ("An abstraction," said Whitehead, "is nothing other than an omission of part of the truth.")

This allows us to better understand the essential incompleteness of knowledge and modelling, and the limits of human intelligence.  Paradoxically such a recognition makes us more intelligent.

This brings us back to the poststructuralists' territory of political liberation, after a fashion.  Yes, every culture and every group constructs its own models about the world and their place in it.  But these are simply isomorphic structures: not artificial "social constructs" with no relation to any "objective" reality.  But as isomorphic structures they are all essentially partial and incomplete;  and no one model has, in totality, an advantage over others.  It may have advantages in some areas -- greater isomorphic fidelity, we might say -- but may just as easily carry disadvantages in other areas.

Therefore a culture that imposes its own modelling system over others does so with no justification other than the old Platonic fallacy of justice as the will of the stronger.

On the other hand, such a view does suggest another kind of modelling system, a pluralist one that allows diversity of sub-systems.  The meta-system would require some reasonable allocation of free rein within each sub-system, with an over-arching regime of agreed human rights.  

Moreover, human beings can join together to construct meanings not only in representation, but in reality.  Constructed forms can be not merely stand-alone iconic representations, but connective portals to richer meaning and quality.  They can exploit deep symmetries, resonances, connective complexity.  They can embody greater feeling, and "spirit".  They can exploit the adaptive characteristics of nature, and attain its stability and sustainability.  They can knit together a fabulously rich new kind of human culture.    

That, I assert, can be an enormously powerful thing.