The conceptual metaphor theory of cognition was first detailed by Lakoff and Mark Johnson in Metaphors We Live By. There they define metaphor in the following way:
The essence of metaphor is understanding and experiencing one kind of thing in terms of another. (p. 5)
This seems fairly normal, but the definition is built around a controversial thesis, namely that our conceptual systems are themselves metaphorical. Here is how they put it:
Metaphor is for most people a device of the poetic imagination and the rhetorical flourish--a matter of extraordinary rather than ordinary language. Moreover, metaphor is typically viewed as characteristic of language alone, a matter of words rather than thought or action. For this reason, most people think they can get along perfectly well without metaphor. We have found, on the contrary, that metaphor is pervasive in everyday life, not just in language but in thought and action. Our ordinary conceptual system, in terms of which we both think and act, is fundamentally metaphorical in nature. (p. 3)
They explain this view further with the following:
To give you some idea of what it could mean for a concept to be metaphorical and for such a concept to structure an everyday activity, let us start with the concept ARGUMENT and the conceptual metaphor ARGUMENT IS WAR. This metaphor is reflected in our everyday language by a wide variety of expressions:
ARGUMENT IS WARYour claims are INDEFENSIBLE.
He ATTACKED EVERY WEAK POINT in my argument.
His criticisms were RIGHT ON TARGET.
I DEMOLISHED his argument.
I've never WON an argument with him.
You disagree? Okay, SHOOT!
If you use that STRATEGY, he'll WIPE YOU OUT.
He SHOT DOWN all of my arguments.
It is important to see that we don't just talk about arguments in terms of war. We can actually win or lose arguments. We see the person we are arguing with as an opponent. We attack his position and we defend our own. We gain and lose ground. We plan and use strategies. If we find a position indefensible, we can abandon it and take a new line of attack. Many of the things we do in arguing are partially structured by the concept of war. Though there is no physical battle, there is a verbal battle, and the structure of an argument -- attack, defense, counterattack, etc. -- reflects this. It is in this sense that the ARGUMENT IS WAR metaphor is one that we live by in this culture; it structures the actions we perform in arguing. (p. 4)
The book, and much of their subsequent work, is full of examples like the ARGUMENT IS WAR metaphor, such as UNCERTAINTY IS UP, UNDERSTANDING IS SEEING, ANGER IS HEATED FLUID IN A CONTAINER, and LOVE IS A JOURNEY (see here for an extended list of conceptual metaphors). In fact, the primary (some would say only) evidence for their theory is the everyday use of statements that fit into these sorts of metaphorical expressions.
A second aspect of Lakoff's theory of conceptual metaphors is that the metaphors themselves are embodied. In other words, our concepts are built metaphorically from direct bodily experience. Embodied experiences that are repeated in our everyday experience (e.g., moving upwards) create what Lakoff calls "image schemas," which can then be used to structure less embodied experiences. Concrete, embodied experiences are therefore the least metaphorical, because they are built from direct experience, while more abstract concepts are structured metaphorically through mappings to more direct bodily experiences. UNCERTAINTY, a fairly abstract concept, is metaphorically structured by the bodily experience of "upwardness," and UNDERSTANDING, another abstract concept, from the bodily experience of seeing. Some concepts (e.g., LOVE) receive their structure from other concepts (e.g., JOURNEY) that are themselves structured metaphorically, from the image schemas of still more concrete (embodied) experiences.
There are several criticisms of this view, all of which together, in my mind, render it indefensible. The first, articulated by Greg Murphy1, notes that Lakoff and Johnson's almost exclusive reliance on linguistic evidence is both equivocal and circular (a common criticism of linguistic evidence in general). Is our speech metaphorical because our concepts are, our concepts metaphorical because our speech is, or is there some mediating factor? Lakoff and Johnson's analysis cannot distinguish between these possibilities. While there is some psycholinguistic evidence that our use and understanding of metaphors, idioms, and other types of figurative speech is connected to our conceptual structures, there is little or no empirical evidence that these concepts are, themselves, metaphorical. For Lakoff and Johnson's theory of conceptual metaphor to carry any weight, nonlinguistic evidence is needed. Twenty years into the conceptual metaphor project, it's hard to believe that this sort of evidence is forthcoming.
A second criticism, also from Murphy, argues that "structural similarity" between conceptual domains can account for the linguistic data without recourse to metaphor. Arguments are like wars in certain important ways, and this similarity, along with economical constraints on cognitive and linguistic structures, can explain the use of similar expressions in talking about the two domains. Nothing about the use of the expressions implies deep metaphorical relations between the two domains in our everyday representations of them. In essence, it appears that Lakoff and Johnson are doing what some refer to as "linguistic anthropology." Perhaps the terms used to describe arguments (or war) were once borrowed from the domain of war (or arguments), and thus used metaphorically. However, these once metaphorical terms have become lexacalized within the domain of arguments, and carry little or no connection to their former domain when used in the newer one. Once again, nothing in the linguistic evidence argues against this interpretation.
Murphy also faults conceptual metaphor theory for failing to explain the seemingly arbitrary choice of metaphors in everyday speech. Why do we use some experiences to metaphorically structure concepts, and not others which also bear structural similarity to the target concept? For instance, arguments could also be compared to journeys. Why aren't they? The reply to this criticism from the conceptual metaphor camp is usually that the direction of the metaphors, from more embodied to less embodied concepts, is important in determining what conceptual mappings are chosen. Thus seeing is used to structure our concept of understanding because seeing is a more embodied experience than that of understanding. This reply fails for many reasons, some of which I'll mention in a bit. For now, suffice it to say that the linguistic evidence alone fails to account for the particular metaphors that we find in everyday speech.
A final criticism from Murphy notes that many of the metaphors we use to describe the same concepts in everyday speech are inconsistent with each other. Is love a journey, or is it an opponent? Perhaps it is insanity, or a valuable commodity? Lakoff and Johnson observe that we use each of these metaphors in everyday speech, but Murphy shows that these metaphors often result in inconsistencies that would create concepts of love that contradict each other. This is perhaps Murphy's weakest criticism, as we now understand that concepts are not monolithic, static entities, of a single nature (see here for an argument against the "Natural Kind" view of concepts which views them as a single sort of fairly static representation). However, it does serve to further illustrate the arbitrariness of conceptual metaphor theory. It appears that the reason we have so many ways of talking about love is that, throughout the history of talking about love, people have used many different metaphors. Some of these metaphors have caught on, while others have not. The ones that have caught on have in turn become literal ways of talking about love, or dead metaphors, and the once metaphorical phrases have lost their connections to their original domains.
Two further criticisms not mentioned by Murphy are worth noting. The first involves the role of embodiment in conceptual metaphors, a role that is required for the theory to work (e.g., to explain the seemingly arbitrary choices of metaphors). In short, there is little evidence for this role. Obviously, we are embodied agents, and all of our conceptual representations are influenced by this embodiment, but there is no evidence that this influence is metaphorical, or that the relationships between concepts move in a single direction (from more embodied to less so). In fact, Lakoff's own example, from page 4 of Metaphors We Live By illustrates a conceptual relation that goes in the other direction! How many of us have direct, embodied experience of war? Very few of us, I would imagine. Still, the first and most prominent example used by Lakoff involves the concept ARGUMENT being structured by the concept WAR. I have a great deal of bodily experience with arguments, and none with war, yet I still talk about winning arguments, argument strategies, and defensive and offensive tactics in arguments. How can Lakoff argue that my concept of argument is structured through more direct, embodied experience of war, if I have none? Based on Lakoff's own analysis, I should never be able to learn this structuring of ARGUMENT, without the necessary bodily experience.
The last, and perhaps most important criticism of conceptual metaphor theory, particularly from the perspective of political theorists and practitioners who would want to use the theory to better frame political concepts, is that there it offers very little in the form of mechanisms. How are concepts mapped onto each other? How is structure from one concept carried to another? How are inferences from these structures made? How are these structures represented? Lakoff's theory offers no answers to these questions. Sure, he provides plenty of linguistic examples of the types of mappings (metaphorical, metonymical, polysemic, etc.), and even the types of inferences made, but no description of how any of this occurs. If we want to come up with new frames, and thus new mappings, we are going to need to have some idea of how these things occur. Without it, we are opening ourselves up to the kinds of problems that I mentioned in my last post on Lakoff.
1 Murphy, G. 1996. "On metaphorical representation", Cognition 60: 173-204.
Further Resources on Conceptual Metaphor and Related Theories
Lakoff on Conceptual Metaphor
Women, Fire, and Dangerous Things by George Lakoff
Philosophy in the Flesh : The Embodied Mind and Its Challenge to Western Thought by George Lakoff and Mark Johnson
The Literary Mind: The Origins of Thought and Language
by Mark Turner
The Way We Think: Conceptual Blending and the Mind's Hidden Complexities by Gilles Fauconnier and Mark Turner
The Poetics of Mind : Figurative Thought, Language, and Understanding by Raymond Gibbs Jr.
Mappings in Thought and Language by Gilles Fauconnier
Unless you're really interested in doing research on Lakoff's conceptual metaphor theory, I would recommend skipping all but Mappings in Thought and Language and The Poetics of Mind. Philosophy in the Flesh is particularly bad, and philosophers who read it, especially those familiar with the last 100 years of continental philosophy, will probably find it downright offensive.