Vive la différance

So farewell Jacques Derrida, France's most famous philosopher of recent times, whose work by its nature compounded its own miscomprehension. To understand Derrida, I think you have to see him in the light of structural linguistics and scepticism.
In the 1960s, the over-riding notion of how language worked was based on minimal phonetic pairs, called phonemes. At its most basic level language could be broken down into these pairs s/z, t/d, p/b etc. so that we understood language by these sounds: bat is different to pat is different to pad is different to bad... you get the idea. (This can be seen through tonal distinctions made by the Chinese tones: mă or mā, incomprehensible to many English-speaking ears, or in Castillian Spanish making no distinction between b and v.) Since all language was made up of these minimal pairs, by extension any text could be broken down into linguistic pairs: subject / object, active / passive etc.
Derrida did not wholly subscribe to this view, however, but drawing on sceptical philosophy of suspension of judgement deemed that we understood language not because of these minimal pairs, but because one piece of language was different to another. So cat was different not just to cad but to dog as well. All language is made up of this vast array of differences, so that we understand language with reference to other elements of language; meaning is deferred until it can be conceptualized with reference to other meaning. Derrida coined the term différance to describe this semi-deliberate delay in understanding something until it is distinguished from other things. It was a play on words (it means both difference and deferral) that practically every other academic has since tried to imitate. (There is linguistic evidence of this too, in the way that language evolves: a word used 300 years ago is unlikely to mean the same as it does now: what's the first thing you think of when you see the word web?)
The corollary of such deferral of meaning was that everything you did and everything that influenced you also had an impact on how you understood language. To get to the root meaning of a text therefore, you had to deconstruct it of all these layers of meaning that were sitting atop it: political, cultural, emotional.
Derrida was extensively mis-read, glossed over (as here) and misunderstood, possibly not least by himself, to the extent that some took deconstruction to be a denial of objective fact; though I'm not sure that Derrida ever said this. I think his thought was an asset to the way in which we might choose to view the world, where our preconscious emotions are layered with meaning as we try to express them and the moment we release text for others to read or listen to, they are no longer our own but a construct of the culture in which they are consumed.
A bit like a content management system.