In "Différance," Derrida attempts to draw out the truly radical implications of Saussure’s model of language which Saussure himself failed to realise. He proposes, in a nut shell, that his own notion of différance, derived from Saussure’s own model, more accurately accounts for the true nature of signification than does Saussure’s concept of ‘difference’. Derrida’s interest is in langue, that is, the abstract principles by which any language operates rather than parole (or actual uses of langue). Saussure, you might recall, problematises the conventional understanding of how signs mean. Traditionally, the sign was thought to function referentially and/or expressively. To be precise, implicit in some schemas such as Plato’s (The Republic Book X) was a mimetic view of the sign, that is, it was thought to passively mirror a real object (the referent). Implicit in other schemas such as Longinus’s was the view that the sign expresses the speaker’s or the writer’s pre-given ideas and/or emotions. Sometimes, in schemas such as Locke’s, signs are the vehicle for expressing the ideas which people have in their minds about and which reflect reality. Traditionally, signs were implicitly thought to have a ‘necessary,’ almost magical relationship to that which they designated: it was almost as if only c-a-t and no others could denote the creature that English-speaking peoples call a ‘cat.’

For Saussure, by contrast, signs mean neither by referring to real objects nor expressing pre-given ideas/emotions. If signs are not the verbal mirrors of particular referents or merely vehicles for ideas, how then do signs mean? To answer this, Saussure divides up the hitherto unified sign into two parts: the signifier (or ‘sound-image’) and the signified (or the mental concept which a person has of an external object and, importantly, not the object itself). His point is that particular sounds have historically come to be attached arbitrarily to specific mental concepts through convention not as a result of some ‘necessary’ relationship between a real object and a sign. This raises another question: what exactly causes a particular sound to be attached to a specific concept? Why does c-a-t, for example, signify ‘cat’? Why did not r-e-f-r-i-g-e-r-a-t-o-r come to be attached to the same signified? The answer: the fact that any given language (such as English) takes the form at any particular moment of its history of a synchronic sign system predicated upon what Saussure terms in French ‘différence.’ Within that system, a particular signifier has come to be attached to a given signified simply because distinctly different sounds have come to be attached to other signifieds and so on ad infinitum. The signs which comprise a particular sign-system in this way are linked to each other by a relationship of ‘difference without positive presence,’ as Saussure puts it: c-a-t signifies ‘cat’ because the distinctly different signifier d-o-g is attached to dog and so on. The real animal that we call a cat does not determine the process of signification in any way (as it did in the traditional model of the sign). There are undoubtedly real objects out there but they do not in and of themselves enter the sign system per se.

There are a number of important implications to the foregoing. Firstly, signs, from this point of view, do not exist in a one-to-one correspondence to the things they name. Signs are not the verbal mirror of reality. Secondly, the relationship of difference or distinction between signs which enables signs to mean is responsible for cutting up (Saussure’s word for this is ‘articulating’) reality into binary oppositions. Humans impose these binaries upon the Real which is in and of itself a continuum which knows no such divisions. (For example, why do we unthinkingly assume that the colours black and white are sheer opposites? Why not purple and blue?) Thirdly, signs are not mere vehicles for pre-given ideas. Before humans acquire language, the capacity for cognitive thought exists but formally structured ideas are non-existent. Without language, the mind is a chaos. On the other hand, language without the capacity of humans for thought would itself be merely gibberish. Meaningful thought and its communication occur when the capacity for thought intersects with the use of language.

Of course, meaningful thought is most often communicated via the use of entire sentences rather than words in isolation. Hence, Saussure’s view that any sentence means only because it operates on the basis of two axes simultaneously: the syntagmatic (this refers to the sequence of words that comprise a given sentence and involves question of syntax or grammar) and the paradigmatic (whereby each sign in a sentence is part of the larger sign-system of the language in question and is differentiated from all the other signs which comprise it, i.e. if the sign ‘cat’ is to be found in a given sentence it is because the speaker of this parole did not want to use the sign ‘dog’ from which ‘cat’ is differentiated).

Derrida’s goal is to underscore what he term the metaphysics of presence which informs, paradoxically, Saussure's notion of ‘difference without positive presence.’ For Derrida, Saussure was right to argue that langue operates in a systemic fashion. In other words, signifiers, signifieds and, thus, signs are defined not by their positive content (i.e., the fact that they refer to a real object) but negatively (i.e., by phonic and conceptual differences which issue from the system). It is useful to quote in this regard Saussure’s comment in its entirety as Derrida does:

in language there are only differences. Even more important: a difference generally implies positive terms between which the difference is set up; but in language there are only differences without positive terms. Whether we take the signified or the signifier, language has neither ideas nor sounds that existed before the system, but only conceptual and phonic differences that have issued from the system. The idea of phonic substance that a sign contains is of less importance than the other signs that surround it. (30)

The true implication of all this is that, given the location of the sign within the sign-system, to be precise, its dependency upon other signs in order to generate meaning, the sign is not autonomous, that is, it is not a self-contained unit. As a result, meaning can never be fully present in any given sign. Meaning is not the result simply of the attachment of a given signifier to a particular signified. Rather, as we have seen, the attachment of a particular signifier to a given signified to form a sign is determined by the sign’s relationship to other signs in the sign-system. For this reason, in order to mean at all, signifiers ceaselessly and endlessly gesture towards the other signifiers of a particular sign-system from which they are differentiated. As a result of this, meaning is less ‘self-contained’ within a given sign than it is dispersed or disseminated. (There is undoubtedly a sexual image here designed to suggest the immense fecundity of language and, thus, the probability of ambiguity and misunderstanding.) In short, cat or white depends upon its difference or distinction from all the other signs (e.g. dog or black) in order to signify at all.

Derrida asserts that the relationship which actually binds a sign-system together is not one of pure difference or distinction but, rather, différance. Derrida spells this word in this way in order both to stress his indebtedness to Saussure’s concept of ‘différence’ and to signal that his own use of the term adds something extra or supplementary which is significantly different to it. (Derrida may be said to be Signifyin[g], in Gates’s sense of this term, upon Saussure’s notion of ‘différence.’) Saussure’s term ‘différence’ is predicated solely upon a spatial metaphor for conceptualising the sign-system. Within his scheme of things, you might recall, the sign is located in a purely synchronic system. The term ‘synchronic’ (as opposed to ‘diachronic’) implies the stasis of the sign-system in relation to which any individual sign must be understood. The sign-system is conceived to exist at an artificially isolated moment of the historical development of a particular language. (The sign ‘cool’ as it is used in 1998 is different from what it meant in 1937 because in each case there is a different system of signs in place which accordingly determines the signification of each sign differently.) To put all this another way, the sign is, in Saussure’s schema, part of a system conceptualised solely in spatial, rather than temporal, terms. Each sign means what it does by virtue of the fact that it occupies a clearly different space from its companions in that system.

If Saussure’s term ‘différence’ denotes the distinction between signs which is responsible for signification, Derrida’s term ‘différance’ simultaneously denotes the displacement and the deferral which impedes clarity of signification (hence, the importance of Derrida’s change in spelling). Derrida’s point is that signifiers/phonemes, signifieds/concepts and, thus, signs always already bear within themselves the trace of the other excluded items in a way that undermines the ideal of self-sufficient plenitude which inheres in the very notion of the sign. Consequently, utilising Saussure’s purely spatial metaphor for conceptualising the sign-system, Derrida contends that the meaning of each sign is ‘displaced’ precisely because the sign is not self-contained in its own autonomous space. To signify what it does, the sign is dependent upon the other signs from which it is supposed to be different. However, Derrida also introduces a temporal element into the process of signification arguing that meaning is also always delayed or deferred. He uses the metaphor of a ‘chain’ (rather than that of a spatial ‘system’), borrowed from a Philosopher/Psychoanalyst called Jacques Lacan, to this end. The signification of a particular sign, he argues, is endlessly deferred along a ‘chain’ of signifiers with no endpoint. Cat is differentiated from dog which is differentiated from refrigerator which is differentiated from ox, and so on ad infinitum. Each sign is conceived, within Derrida’s schema, as taking its ‘place’ along a chain or in a sequence in which it is linked both to the sign which precedes it (hence, Derrida speaks of "retentions" [32]) and that which follows (hence, "protentions" [32]). As a result, "each so-called ‘present’ element . . . is related to something other than itself, thereby keeping within itself the mark of the past element, and already letting itself be vitiated by the mark of its relation to the future element" (32).

As a result of these two factors (displacement [spacing] and deferral [temporization]), (the) presence (of the referent itself), the thing-in-itself which the sign is supposed to name and for which the sign is supposed to be a verbal substitute, is continually displaced within the sign-system and endlessly deferred along the chain of signification. Derrida points out that the

sign is usually said to be put in the place of the thing itself, the present thing, ‘thing’ here standing equally for meaning or referent. The sign represents the present in its absence. It takes the place of the present. When we cannot grasp or show the thing, state the present, the being-present, when the present cannot be presented, we signify, we go through the detour of the sign. (28)

As a result of différance, the sign by its very nature thus implies that circulation which defers the "moment in which we can encounter the thing itself, make it ours, consume or expend it, touch it, see it, intuit its presence" (28), as Derrida puts it. The dream of finding the so-called transcendental signifier (the last one in the chain which would have, as such, an unmediated relationship to the real) and thus reaching the end of the endless chain of signification is just that: a dream.

In summary, Derrida demonstrates how Saussure’s notion of difference deconstructs itself (note that I did not write ‘Derrida deconstructs Saussure’s notion of difference’). He brings out the unseen implications of Saussure’s model of the sign in order to underscore its inherent radicalness. Every time one says/writes ‘white,’ one simultaneously implies all the other signs from which it is differentiated (e.g. black) in order for it to mean what it does. Far from being distinct, therefore, each sign exists in a relationship of dependency with the others. The trace of the other signs inheres, as Derrida puts it, in each sign. There are a number of important implications to all this. Firstly, Derrida to some degree turns our attention away from the relationship between sign and referent and towards their relationship with other signs. In order to signify, signs refer, if anything, to other signs. Since one can never attain to the thing-in-itself, Derrideans argue, attention should focus, rather, on the semiological processes by which the ‘thing’ is signified as well as on the ways in which those processes undo themselves. The effect of this on some literary criticism has been an alleged formalism resulting in one form thereof (I am thinking of a school of criticism called the so-called ‘Yale School of Deconstruction’) which has tended, according to some of its harsher opponents, to sever altogether the link between text and context. Secondly, Derrida draws our attention to the fact that all binary opposites (the result of the différence envisioned by Saussure) deconstruct themselves. A seemingly stark and stable contrast like that between black and white is undone by the semiological principle which Derrida calls différance. We would have no concept of black without white or, to put it another way, the meaning of ‘black’ is not fully present in the sign ‘black’ but is deferred, rather, to other signs such as ‘white.’ This deconstruction has tremendous implications for any argument, predicated as these always are upon binary opposition. Derrideans take great joy in searching for the binary opposites at the heart of any argument and showing how these deconstruct themselves, thereby causing the argument to collapse. Given that thinking is impossible without language, the implication of Derrida’s notion of différance is that rational thought or argumentation is a radically unstable affair which ceaselessly undoes itself. All a deconstructionist has to do is to merely trace the ways in which the boundaries between seemingly discrete categories essential to someone’s argument become blurred in and of themselves (as a result of the principle of différance at work in any use of language and not due to anything the deconstructionist is doing) and in this way underscore the aporia or contradictions inherent in that argument. In other words, speakers and writers have intentions (usually predicated upon some form[s] of binary opposition) but these are undermined by the nature of signification as a result of which one’s argument gets all tangled up in subtle or not so subtle contradictions.