Metaphor

    In language, a metaphor (from the Greek: metapherin rhetorical trope) is defined as a direct comparison
    between two or more seemingly unrelated subjects. In the simplest case, this takes the form: "The [first subject]
    is a [second subject]." More generally, a metaphor casts a first subject as being or equal to a second subject in
    some way. Thus, the first subject can be economically described because implicit and explicit attributes from the
    second subject are used to enhance the description of the first. This device is known for usage in literature,
    especially in poetry, where with few words, emotions and associations from one context are associated with
    objects and entities in a different context.

    Within rhetorical theory metaphor is generally considered to be a direct equation of terms that is more forceful
    and assertive than an analogy, although the two types of tropes are highly similar and often confused. One
    distinguishing characteristic is that the assertiveness of a metaphor calls into question the underlying category
    structure, whereas in a rhetorical analogy the comparative differences between the categories remain salient
    and acknowledged. Similarly, metaphors can be distinguished from other closely related rhetorical concepts such
    as metonymy, synecdoche, simile, allegory and parable.

    Aspects of metaphor
    A metaphor, according to I. A. Richards in The Philosophy of Rhetoric (1936), consists of: the tenor and vehicle.
    The tenor is the subject to which attributes are ascribed. The vehicle is the subject from which the attributes are
    borrowed.

    All the world's a stage,
    And all the men and women merely players
    They have their exits and their entrances; — (William Shakespeare, As You Like It, 2/7)
    This well known quote is a good example of a metaphor. In this example, "the world" is compared to a stage, the
    aim being to describe the world by taking well-known attributes from the stage. In this case, the world is the
    tenor and the stage is the vehicle. "Men and women" are a secondary tenor and "players" is the vehicle for this
    secondary tenor.

    The metaphor is sometimes further analyzed in terms of the ground and the tension. The ground consists of the
    similarities between the tenor and the vehicle. The tension of the metaphor consists of the dissimilarities
    between the tenor and the vehicle. In the above example, the ground begins to be elucidated from the third line:
    "They have their exits and their entrances." In the play, Shakespeare continues this metaphor for another
    twenty lines beyond what is shown here - making it a good example of an extended metaphor.

    The corresponding terms to 'tenor' and 'vehicle' in George Lakoff's terminology are target and source. In this
    nomenclature, metaphors are named using the convention "target IS source", with the word "is" always
    capitalized; in this notation, the metaphor discussed above would state that "humankind IS theater".

    Types of metaphor
    An extended metaphor, or conceit, sets up a principal subject with several subsidiary subjects or comparisons.
    The above quote from As you like it is a good example. The world is described as a stage and then men and
    women are subsidiary subjects that are further described in the same context.
    A mixed metaphor is one that leaps, in the course of a figure, to a second identification inconsistent with the first
    one. Example: "He stepped up to the plate and grabbed the bull by the horns," where two commonly used
    metaphors are confused to create a nonsensical image.

    A dead metaphor is one in which the sense of a transferred image is not present. Example: "to grasp a concept"
    or "to gather you've understood." Both of these phrases use a physical action as a metaphor for understanding
    (itself a metaphor), but in none of these cases do most speakers of English actually visualize the physical action.
    Dead metaphors, by definition, normally go unnoticed. Some people make a distinction between a "dead
    metaphor" whose origin most speakers are entirely unaware of (such as "to understand" meaning to stand
    underneath a concept), and a dormant metaphor, whose metaphorical character people are aware of but rarely
    think about (such as "to break the ice"). Others, however, use dead metaphor for both of these concepts, and
    use it more generally as a way of describing metaphorical cliché.

    An epic or Homeric simile is an extended metaphor containing details about the vehicle that are not, in fact,
    necessary for the metaphoric purpose. This can be extended to humorous lengths, for instance: "This is a crisis.
    A large crisis. In fact, if you've got a moment, it's a twelve-story crisis with a magnificent entrance hall, carpeting
    throughout, 24-hour porterage and an enormous sign on the roof saying 'This Is a Large Crisis.'" (Black Adder)
    A synecdochic metaphor is one in which a small part of something is chosen to represent the whole so as to
    highlight certain elements of the whole. For example "a pair of ragged claws" represents a crab in Eliot's Love
    Song of J. Alfred Prufock. Describing the crab in this way gives it the attributes of sharpness and savagery
    normally associated with claws.
    Other types of metaphor have been identified as well, though the nomenclatures are not as universally accepted:

    An active metaphor is one which by contrast to a dead metaphor, is not part of daily language and is noticeable
    as a metaphor. Example: "You are my sun."
    A complex metaphor is one which mounts one identification on another. Example: "That throws some light on the
    question." Throwing light is a metaphor and there is no actual light.
    A compound or loose metaphor is one that catches the mind with several points of similarity. Example: "He has
    the wild stag's foot." This phrase suggests grace and speed as well as daring.
    An absolute or paralogical metaphor (sometimes called an antimetaphor) is one in which there is no discernible
    point of resemblance between the tenor and the vehicle. Examples:

    "The couch is the autobahn of the living room."
    "Six Flags is the aquarium of roller coasters."

    An implicit metaphor is one in which the tenor is not specified but implied. Example: "Shut your trap!" Here, the
    mouth of the listener is the unspecified tenor. In poetry, an Implicit metaphor is a metaphor implied by the text.
    Example: In John Donne's "The Bait" there is an implicit fishing metaphor throughout the entire poem.
    A submerged metaphor is one in which the vehicle is implied, or indicated by one aspect. Example: "my winged
    thought". Here, the audience must supply the image of the bird.
    A simple or tight metaphor is one in which there is but one point of resemblance between the tenor and the
    vehicle. Example: "Cool it". In this example, the vehicle, "cool", is a temperature and nothing else, so the tenor,
    "it", can only be grounded to the vehicle by one attribute.

    A root metaphor is the underlying association that shapes an individual's understanding of a situation. Examples
    would be understanding life as a dangerous journey, seeing life as a hard test, or thinking of life as a good
    party. A root metaphor is different from the previous types of metaphor in that it is not necessarily an explicit
    device in language, but a fundamental, often unconscious, assumption.
    Religion provides one common source of root metaphors, since birth, marriage, death and other universal life
    experiences can convey a very different meaning to different people, based on their level or type of religious
    conditioning or otherwise. For example, some religions see life as a single arrow pointing toward a future
    endpoint. Others see it as part of an endlessly repeating cycle. In his book World Hypotheses, the philosopher
    Stephen Pepper coined the term and proposed a theory of four ultimate root metaphors--formism, mechanism,
    organicism, contextualism.

    A conceptual metaphor is an underlying association that is systematic in both language and thought. For
    example in the Dylan Thomas poem "Do Not Go Gentle into That Good Night," the conceptual metaphor of "A
    Lifetime is a Day" is repeatedly expressed and extended throughout the entire poem. The same conceptual
    metaphor is the key to solving the Riddle of the Sphinx: "What goes on four legs in the morning, two legs at
    midday, and three in evening? --A man." Similar to root metaphors, conceptual metaphors are not only expressed
    in words, but are also habitual modes of thinking underlying many related metaphoric expressions.
    Because they both underlie more than just the surface metaphoric expression, root metaphors and conceptual
    metaphors are easily confused. For example: In the United States, both conservatives and liberals use 'family'
    metaphors for the national politics, though in different ways. Both types of usage would ultimately resolve to
    "organic" root metaphors in Pepper's nomenclature, while Lakoff would distinguish between several different
    varieties of the "A Nation is A Family" metaphor.

    A dying metaphor Coined in his essay Politics and the English Language George Orwell calls a dead metaphor
    one that has been worn out and is used because it saves people the trouble of developing original language to
    express an idea. In short, it is cliché. Example: Achilles' heel. Orwell suggests that writers scan their work for
    such dying forms that they have 'seen regularly before in print' and replace them with alternative language
    patterns.
    The category of metaphor can be further considered to contain the following specialized subsets:

    allegory: An extended metaphor in which a story is told to illustrate an important attribute of the subject
    catachresis: A mixed metaphor (sometimes used by design and sometimes a rhetorical fault)
    parable: An extended metaphor told as an anecdote to illustrate or teach a moral lesson

    Etymology
    Originally, metaphor was a Greek word meaning "transfer". The Greek etymology is from meta, implying "a
    change" and pherein meaning "to bear, or carry".

    In modern Greek, the word metaphor also means transport or transfer.

    Metaphor and Simile
    Metaphor and simile are two of the best known tropes and are often mentioned together as examples of
    rhetorical figures. Metaphor and simile are both terms that describe a comparison: the only difference between a
    metaphor and a simile is that a simile makes the comparison explicit by using "like" or "as." The Columbia
    Encyclopedia, 6th edition, explains the difference as:

    a simile states that A is like B, a metaphor states that A is B or substitutes B for A.
    According to this definition, then, "You are my sunshine" is a metaphor whereas "Your eyes are like the sun" is a
    simile. However, some describe similes as simply a specific type of metaphor (see Joseph Kelly's The Seagull
    Reader (2005), pages 377-379); in this case, metaphor is the umbrella term for making comparisons between
    unlike concepts, and simile describes the figure where one makes the comparison explicit.

    Usually, similes and metaphors could easily be interchanged. For example remove the word 'like' from William
    Shakespeare's simile, "Death lies on her, like an untimely frost," and it becomes "Death lies on her, an untimely
    frost," which retains almost exactly the same meaning.

    Despite the similarity of the two figures, the distinction between them is often focused upon when the terms are
    introduced to students. "Not knowing the difference between a simile and a metaphor" is sometimes used as a
    euphemism for knowing little about rhetoric or literature, and many lists of literary terms define metaphor as "a
    comparison not using like or as", showing the emphasis often put on this distinction.

    Although in practice their use is often synonymous, in a rigorous sense, their meanings can be understood to be
    quite different. Whereas simile explicitly describes a comparison, metaphor asserts an identity. A simile always
    expresses something trivially true (anything can be likened to anything else), whereas a metaphor always
    expresses something patently false (which the listener must then make sense of). In other words, one could
    argue that when listening to an active metaphor, the listener always visualizes something false before analyzing
    the phrase metaphorically. On the other hand, a simile requires a different kind of analysis: the listener is
    explicitly asked to compare two objects rather than being forced to when confronted with an otherwise
    nonsensical phrase. In both cases, this analysis depends on the assumption that listeners think of the literal
    meaning first, which is only guaranteed when a comparison is fresh.

    There are cases where the use of a simile rather than a metaphor makes a clear difference in meaning or listener
    expectation. Using a simile as opposed to a metaphor can clarify an analogy by calling out exactly what is being
    compared. "He had a posture like a question mark" (Corbett, Classical rhetoric for the modern student (1971),
    page 479) has one possible interpretation, that the shape of the posture is that of a question mark, whereas
    "His posture was a question mark" has at least a second interpretation, that the reason for the posture is in
    question. Using a simile rather than a metaphor can add meaning by calling attention to the process of
    comparison, as in, "A woman without a man is like a fish without a bicycle."

    The point is not to compare a person to a fish, but to ask the reader to consider how the woman is like the fish.
    Similarly, when speakers wish to call attention to a particularly unexpected comparison, they typically use a simile
    rather than a metaphor, as in the Magnetic Fields line, "When I'm with you, it's like I'm on the moon; I can hardly
    breathe but I feel lighter." Finally, similes are often more convenient than metaphors when analogizing actions
    as opposed to things: "Wide sleeves fluttering like wings" (Marcel Proust) does not translate easily from simile to
    metaphor. A final difference is that in practice, often-used metaphors can "wear away" into dead metaphors as
    listeners come to learn metaphorical meanings by rote rather than making sense of seemingly nonsensical
    assertions, whereas a simile, because it explicitly calls attention to the act of comparison, is not as susceptible to
    the loss of metaphoricity. Thus, although for fresh comparisons metaphors are typically seen as "stronger" than
    similes, similes can retain their metaphorical nature more consistently than metaphors precisely because they are
    not likely to be reanalyzed as secondary meanings of words or phrases.

    Metaphors in literature and language
    Metaphor is present in written language back to the earliest surviving writings. From the Epic of Gilgamesh (one
    of the oldest Sumerian texts):

    My friend, the swift mule, fleet wild ass of the mountain, panther of the wilderness, after we joined together and
    went up into the mountain, fought the Bull of Heaven and killed it, and overwhelmed Humbaba, who lived in the
    Cedar Forest, now what is this sleep that has seized you? - (Trans. Kovacs, 1989)
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