An interesting entry for irony in H. W. Fowler's Modern English Usage (revised and edited by Sir Ernest Gowers, 1965):
Irony is a form of utterance that postulates a double audience, consisting of one party that hearing shall hear and shall not understand, and another party that, when more is meant than meets the ear, is aware both of that more and of the outsiders' incomprehension.
1. Socratic ironywas a profession of ignorance. What Socrates represented as an ignorance and a weakness in himself was in fact a non-committal attitude towards any dogma, however accepted or imposing, that had not been carried back to and shown to be based upon first principles. The two parties in his audience were, first, the dogmatists moved by pity or contempt to enlighten this ignorance, and secondly, those who knew their Socrates and set themselves to watch the familiar game in which learning should be turned inside out by simplicity.
2. The double audience is essential also to what is called dramatic irony, i.e., the irony of the Greek drama. That drama had the peculiarity of providing the double audience--one party in the secret and the other not--in a special manner. The facts of most Greek plays were not a matter for invention, but were part of every Athenian child's store of legend; all the spectators, that is, were in the secret beforehand of what would happen. But the characters, Pentheus and Oedipus and the rest, were in the dark; one of them might utter words that to him and his companions on the stage were of trifling import, but to those who hearing could understand were pregnant with the coming doom. The surface meaning for the dramatis personae, and the underlying one for the spectators; the dramatist working his effect by irony.
3. And the double audience for the irony of Fate? Nature persuades most of us that the course of events is within wide limits foreseeable, that things will follow their usual course and that violent outrage on our sense of the probable or reasonable need not be looked for. These "most of us" are the uncomprehending outsiders; the elect or inner circle with whom Fate shares her amusement at our consternation are the few to whom it is not an occasional maxim, but a living conviction, that what happens is the unexpected.
That is an attempt to link intelligibly together three special senses of the word irony, which in its more general sense may be defined as the use of words intended to convey one meaning to the uninitiated part of the audience and another to the initiated, the delight of it lying in the secret intimacy set up between the latter and the speaker. It should be added, however, that there are dealers in irony for whom the initiated circle is not of outside hearers, but is an alter ego dwelling in their own breasts.
For practical purposes a protest is needed against the application of "the irony of Fate," or of "irony" for short, to every trivial oddity: But the pleasant note changed to something almost bitter as he declared his fear that before them lay a "fight for everything we hold dear"--a sentence that the groundlings by a curious irony were the loudest in cheering (oddly enough). / "The irony of the thing" said the dairyman who now owns the business "lies in the fact that after I began to sell good wholesome butter in place of this adulterated mixture, my sales fell off 75 per cent" ("It's a rum thing that..." seems almost adequate). The irony of Fate is, in fact, to be classed now as a hackneyed phrase.
I experienced a degree of mild shock that the "double-audience" aspect of irony was not one I had considered in quite this way before, though perhaps I should have; have I been missing one of the most well-rehearsed commonplaces of irony all this time? It has simply never occurred to me to project what I considered to be the special circumstance of dramatic irony, that is the uneven economy of knowledge wherein one party is aware of something that another is not, onto irony writ large. Fowler treats dramatic irony, in fact, as the second of "three special senses" of irony "in its more general sense," rather than breaking irony down into three related but separate varieties, as I have always believed to be the standard paradigm:
1. classical or rhetorical irony (saying the opposite of what one means, i.e., with sarcasm or mock ingenuousness, which I would consider as encompassing Socratic irony)
2. dramatic irony
3. "the irony of Fate," or "Romantic" or "cosmic" irony, or just "irony" (events playing out in such a way as to constitute an apparently pointed reversal or deflation of expectations)
One might also consider the extension of this third sense into "postmodern irony" as a wholly new fourth sense, which Fowler naturally could not have included, writing in 1926 (I'm assuming the entry is his and not a substantial revision by Gowers). More on this difficult and vague term later.
Two things interest me particularly about Fowler's entry. First, and most trivially, I am surprised that he demotes the use of "irony" in situations where it means, in his words, "oddly enough" or "a rum thing" to the status of what we would now classify as "Alanis Morrisette irony." In both of the examples of abuses he supplies, "irony" seems perfectly appropriate to me, as I'm guessing it would to most contemporary readers who have some informed familiarity with the concept. The scene of the "groundlings" cheering the speaker is a little obscure, but as far as I can tell, the irony consists in the fact that the persons who cheer the loudest are the ones most likely to be used as cannon fodder in the impending "fight." If that's not it, it's clearly something structurally comparable. The second example seems even more reasonable: the dairyman's good-faith efforts to upgrade his inferior product are met with a loss of profits, as though the universe (or "Fate") were mocking the logic by which his commendable business practice might be expected to be rewarded. Fowler is either unable to see how these examples satisfy his double-audience criterion, or he has some additional, more exacting requirement in mind that I have not grasped.
Second, I'm intrigued by the idea that irony always entails the exclusion of part of its audience from the discourse of knowledge. The wording of Fowler's account, I believe, somewhat overstates this principle, relying on some Procrustean distortions to accommodate it to his definitions, as when he must posit the dramatis personae of Greek drama as part of the audience in order to maintain his conceptual model. Fowler appears almost at times to claim that when a speaker makes a rhetorically ironic statement such as "my opponent must be very proud of himself" (in a situation where the opponent, say, is guilty of criminal mismanagement of charity funds), this speaker really expects some part of the audience to interpret the statement as sincere praise. He manages to escape this absurdity with the concession "that there are dealers in irony for whom the initiated circle is not of outside hearers, but is an alter ego dwelling in their own breasts," but in doing so he suggests that these rarified "dealers" are to be thought of as aberrations from a normative ideal form of irony.
I'm going to give Fowler the benefit of the doubt, however, and conjecture that if he were alive and able to respond to this last objection, he would point out that I am taking him too literally, and that I am treating his subtle stylistic mordancies as myopic lapses--that, as a matter of fact, I am revealing myself as a member of the uninitiated part of the audience for his own irony. And that in itself would be quite ironic (or "a rum thing," or something). We can easily enough adjust his terms to understand him as saying that the double audience for irony is understood not as an actual distribution of persons, some of whom are in on the ironic secret and some who are not, but as a conceptual fiction: all that is necessary is that we are able to imagine an audience that doesn't get it. In the case of dramatic irony, the characters on stage can be seen as the embodied form of such a virtual audience.
Furthermore, I want to take Fowler's formula seriously as a way of describing the ideological function of irony: a social-discursive equation in which there must always be an excluded audience. Irony is, by this account, an inherently "elitist" mode of communication. Or rather, it mimics elitism in order to make a point, which in some cases amounts to real elitism. If I have to act like I'm talking over your head as a way of dramatizing a certain kind of social interaction, it is bound at times to have the incidental effect of you getting your head talked over for real. This is the irony of irony: in only pretending to exclude a part of its audience, with the benevolent aim of "praising" the entire audience for its ability to perceive this pretense, it cannot avoid occasionally performing genuine exclusions. This becomes proportionately more the case as the irony becomes subtler and more complex, and is further complicated by the inevitable situations in which the point of the view being conveyed through ironic means is not one that is shared by all the members of a given audience.
This brings us back to "postmodern irony." I have tremendous difficulty in getting even the most general sense of this concept across to students. My theory is that this is partly because the social and political conditions which are targeted by postmodern irony (if it is even possible to apply a term with such bold connotations of purpose and intention as "targeted" to something as concerned with the radical absence of agency as postmodern irony) are just those conditions under which today's students are held as constrained subjects, unable to avail themselves of the potentially enlightening perspective afforded by the ironic viewpoint, possibly the only viewpoint via which they would be able to register the existence of those conditions in the first place. What is uniquely ironic about postmodern irony* is that the earlier ratio of classical irony is reversed: whereas in classical irony, the actual audience (as opposed to fictional persons on a stage or imagined interlocutors in a dialogue) is mostly composed of informed hearers, in postmodern irony the actual audience is quite likely to be at a loss, while the text (there may no longer be any speaker as such) continues to address with great familiarity and confidence its understanders, who are equally likely to be purely virtual. How is this ironic? Simply in that, in its risking the historical failure of irony's originary ideal--the cultivation of understanding in an enlightened demos--it comes the closest to irony's founding fiction, the fiction of a communication that does not say what it says, that cannot be heard by those for whom it is spoken.
* I am not directly concerned here with that other irony of postmodern irony: that, in its less sophisticated manifestations (I'm thinking of something like a McSweeney's aesthetic), it is reduced to a gesture that has no awareness of its purpose, or even of the kind of purpose it might be thought to have by someone who was concerned with it having one, while it acts as though it does have just such an awareness, feeling safe in the conviction that it is so difficult to tell the difference between postmodern irony that does have such an awareness and postmodern irony that does not that it can never be proven to be unaware (and perhaps reassuring itself with the thought that it does have this much awareness: the awareness that it is supposed to be aware of something which it in fact does not have, and that maybe this little bit of semi-awareness is all it was ever really required to have anyway.