The unconscious, according to Lacan, has to be understood as a chain of signifiers. The central term in this definition is of course, the signifier. This term has to be understood in an active sense: the (linguistic) signifier must be thought of as something that cuts actively into something else that is not yet structured, in the strict sense, and in so doing gives rise to meaning. A few examples will illuminate this idea. It is known that Lacan attaches great importance to fatherhood, and to what he calls the “Name-of-the-Father”. But what is a father? At first sight it seems the answer to this question is readily available. Is not the father simply the begetter of the child? Nevertheless, it would appear from anthropological research that the matter is somewhat more complicated than we usually think. Certain primitive tribes ascribe pregnancy not to coitus with this or that man, for example, but rather to an encounter with spirits in an out-of-the-way place. One need not infer from this that the members of the tribe have no notion of the connection between coitus and pregnancy. This seems rather unlikely. What is at stake here is not so much the question of whether the members of the tribe do or do not know that there can be no pregnancy without coitus, but rather that of whether there exists in the symbolic system a signifier that expresses the idea that the one with whom the woman has coitus is also the father of the child that she bears. In other words, it turns out that the connection between procreation and fatherhood is decided on the level of the symbolic system; it is a question of whether there is a signifier in the symbolic system that articulates this connection. According to Lacan, it follows from this that the signifier is not merely the reproduction of a previously given order. On the contrary, it actively institutes a function - fatherhood - that clearly cannot be directly derived from the facts of experience.
A second example1 might further clarify the meaning and importance of the signifier - the distinction between “man” and “woman.” Few will want to contest that there is indeed such a distinction. Nevertheless, if we try to found [sic] this difference exclusively in reality, we will be disappointed. As much as we might endeavor to justify this distinction in terms of various feelings, patterns of thinking, and so on, we will never find anything more than gradual differences. Yet we are not a bit “man” and a bit “woman” (or vice versa), but either “man” or “woman” - we are one or the other. This absolute difference does not exist in (lived) reality, which knows only gradual distinctions. Even a reference to biological data is of little help here. Certainly, it is difficult to deny that relevant biological differences exist between “men” and “women,” but even these differences seem to offer no satisfactory explanation for the fact that we admit, without hesitation, to belonging to one or the other category. That I am a “man” or a “woman” - the one or the other - is not a pure biological given. On the contrary, such a strict order, on the basis of which we have simply to “choose” one or the other category, only comes about when the symbolic system “impresses” itself, as it were, upon (biological) reality and upon lived experience. The strict difference between “man” and “woman” comes to us from language, as do all other distinctions by which reality is for us ordered and receives it meaning (for example, the distinction between human and animal, between human and gods, etc.). In Lacan’s terms, these distinctions come to us from the order of signifiers, and they must therefore be understood as an actively structuring principle. Lacan has a name for this articulated system of differential (linguistic) distinctions that lays down for us the law in accordance with which we can perceive reality as meaningful: the symbolic. The symbolic is the order of language and of the law.2 Lacan often calls this order the Other (l’Autre).3
Thus it also becomes clear why we said, in our exposition of Freud above, that the expression “reality outside of us” requires further consideration, and cannot simply be accepted as it stands. The world in which we carry on our everyday existence is always already structured by the signifiers of language. The world in which we shape our lives receives its form from our expectations, intentions, representations, and so on, and these are themselves structured in turn by the symbolic systems that determine us (for example, in articulating the difference between man and woman). At the very least, then, the opposition between language and the thing about which it speaks is more complex than we suggested above, and than Freud sometimes seems to think. The world about which we speak and in which we live is no “brute” reality; it is itself already mediated and structured by the signifiers of language, which allow it to appear as a meaningful and differentiated environment (Umwelt).
The signifier actively institutes meaning. Language does not simply reflect reality; it is not the expression of a previously given order. The reality in which we carry on our existence must, on the contrary, be understood in a pregnant sense as the effect of the order of signifiers. In this context, Lacan points out that signifiers are essentially determined diacritically or differentially. In other words, they signify primarily on the basis of their difference from other signifiers and not, for example, by referring to a non-linguistic reality. Let us return to our example of the difference between “man” and “woman.” It is clear that the signifier “man” only has meaning as opposed to the signifier “woman” - for what could “man” mean without “woman”? The signifiers “man” and “woman” receive further meaning from a complex network of references in which signifiers such as “human,” “animal,” and “plant,” for example, hold a central place. The meaning of a signifier is in the first place dependent upon the linguistic context of which it is a part. Moreover, the fact that a signifier only receives meaning from a complex network of signitive references immediately implies, for Lacan, that the meaning of a signifier changes according to the context in which it is taken up. When an analysand says in an analytical session, Je vais à la mer (“I am going to the sea”), the analyst might hear, Je vais à la mère (“I am going to the mother”), basing her interpretation on other associations that the analysand has formulated in the course of this or other sessions. A second example can perhaps make the point somewhat clearer. Some years ago, for professional reasons, I opened a bank account in Holland, and the bank clerk asked if I had any “titles.” I replied that I did, but immediately added that I wanted to keep them in Belgium, where I was living at the time. The man looked at me strangely, and asked me if the “titles” were not valid in Holland. After a bit of talking back and forth, it turned out that he had meant academic titles, while I, because of my Belgian background, had understood “titles” in the sense of the French titres (“financial securities”).4 Just as the associative context determined the meaning of the signifier mer/mère (“sea”/“mother”) in the first example, so here the meaning of the signifier “title” changes depending on whether it is to be understood in an academic context or an economic one. The production of meaning is thus in principle a process that cannot be closed off. There is no ultimate context that could, as it were, embrace all contexts and so bring the production of meaning to completion.
To some extent, we can also understand now why Lacan says that his thesis “the unconscious consists of a chain of signifiers” is in agreement with the basic theses of the Freudian oeuvre. According to Freud, the unconscious is not of the order of language because the unconscious does not know any reference to reality, and it is precisely language that introduces this reference. Lacan’s differential definition of the signifier, however, implies that language cannot be understood primarily as a reference to a reality outside of it, as Freud had thought. On the contrary, the meaning of a term is determined by its place in the system; it is the product of the “play of signifiers.” Just as the Freudian “thing-presentations” combine with each other and generate effects without taking reality into account, so too the Lacanian “play of signifiers” is not determined by a self-sufficient, pre-given referent. Both the Freudian and the Lacanian unconscious, as it were, put external reality out of play. (7-13)
 In what follows we give as an example of signifiers the words “man,” “woman,” etc. Later we will have to nuance this. Signifiers are not in the first place words, but the significant differences that are articulated by phonology.
 Later we will specify this as the law of the father.
 The term “Other” in Lacan does not refer exclusively to the order of language and the law as such. Lacan also often uses this term to indicate the unconscious. For the unconscious is also of the order of language. Furthermore, he also calls other “persons” l’Autre insofar as they represent the order of language and the law.
 To understand this example the reader should know that both the author and the bank clerk were speaking Dutch. The confusion arose because more legal terms derived from French are used in the Dutch spoken in Belgium (Flemish)
Van Haute, Philippe. Against Adaptation: Lacan's "Subversion" of the Subject. Trans. Paul Crowe and Miranda Vankerk. Other Press 2002.
Works and Days