What is the difference between an analogy and a metaphor?

"Time is money" (Franklin, Advice to a Young Tradesman, 1748) is a metaphor: it asserts that one thing is another and stops, leaving the reader to supply the bridge. The same comparison made as an analogy spells the bridge out. Time is like money in that you can save it, spend it, waste it, budget it, run out of it, and account for it, and so the reasoning that applies to one applies to the other (the worked-out form Lakoff and Johnson trace in Metaphors We Live By, 1980). A metaphor compresses; an analogy unfolds. The complication that pulls the binary apart is what happens when a metaphor stops being one line.

How do you tell which one you are writing?

Ask one question of the comparison in front of you: does the sentence assert identity and leave it there, or does it state the parallel and walk through why the comparison holds?

Count what is explicit on the page. A metaphor names the source (the thing you are comparing to) and lets it stand in for the target (the thing you are talking about); the relation between them is implicit, supplied by the reader. An analogy names the source, names the target, names the relation, and often names what the relation lets you conclude.

Run the test on three sentences.

Sentence	Metaphor or analogy	Why
"All the world's a stage, / And all the men and women merely players" (Shakespeare, As You Like It, c. 1599)	Metaphor	Asserts identity (world = stage) and stops. The relation, what the comparison gives the reader, is left implicit.
"Argument is war: you defend positions, attack claims, concede ground, win or lose, and your strategy can collapse" (the worked mapping in Lakoff and Johnson, Metaphors We Live By, 1980)	Analogy	Names source (war), target (argument), and four explicit points of correspondence. The reasoning is on the page.
"Hope is the thing with feathers / That perches in the soul, / And sings the tune without the words, / And never stops at all" (Dickinson, c. 1861)	Borderline	Begins as a one-line metaphor (hope = bird), then specifies perch, song, and persistence. As the figure extends, it acquires the structure of an analogy.

The third row is the case the binary stops describing well.

Where does the line actually fall?

Metaphor is a trope, a figure of meaning. It swaps the target for the source and asks the reader to feel the transfer. Tropes operate on what words mean; schemes operate on how words are arranged. Metaphor is the canonical trope: "Juliet is the sun" works because sun is doing semantic work it does not normally do, and the reader registers the substitution.

Analogy is something else: a structural argument. It names a source domain (a muscle, a flowing river, a chess game), names a target domain (the brain, an economy, a war), names the relation between them, and licenses an inference from one to the other. The argument has the form because the source behaves this way and the target resembles the source in the relevant respects, the target behaves the same way.

Aristotle, in the Rhetoric (3.10), treats metaphor as the transfer of a name from one thing to another, and he prizes it as the move that makes prose feel alive. The structural account of analogy is the one cognitive scientists like Dedre Gentner have made explicit in the last forty years: analogy is the systematic mapping of relations between two domains, not the mapping of surface features. Hofstadter takes the same view in Surfaces and Essences (2013), where analogy is treated as the engine of human thought, not as decoration.

The practical consequence: a metaphor can be wrong in a way an analogy cannot. A metaphor that does not land just falls flat. An analogy can be checked: do the relations actually carry across, or have you mapped surface features and missed the structure?

When does an extended metaphor become an analogy?

The binary holds for one-line figures. It dissolves as the figure unfolds across a paragraph.

Take Donne's compass in "A Valediction: Forbidding Mourning" (1633). Two lovers parted by distance are compared to the two legs of a draftsman's compass:

If they be two, they are two so As stiffe twin compasses are two, Thy soule the fixt foot, makes no show To move, but doth, if th'other doe.

The figure opens as a metaphor: the lovers are two legs of a compass. Then Donne keeps going. He names which lover is the fixed foot. He names what the fixed foot does (leans toward the other as it travels, returns upright when it comes home). He names what this tells the reader about the relationship (the lovers' connection holds across distance because one of them remains the still point). By the end of the conceit the figure has named the source, the target, three points of correspondence, and the inference. It is doing what an analogy does.

This is the move Renaissance critics named the conceit, the extended figure that develops a comparison across many lines. Structurally, a fully developed conceit is an analogy made in poetry instead of prose. The same thing happens in modern writing: a journalist who opens a piece "The American economy is a hot-air balloon" and then spends three paragraphs on the burner, the envelope, and the wind has written a one-line metaphor followed by an analogy of the same comparison.

The line between the two figures is real for one-line work and fades as the figure grows. Both forms are doing the same thing at different magnifications. A metaphor compresses the analogy and trusts the reader to expand it. An analogy expands the metaphor and does the expansion on the page.

Did you know? Aristotle, in the Poetics (21), classifies analogy (proportional metaphor: A is to B as C is to D) as one of the four kinds of metaphor. The classical tradition treated analogy as a species of metaphor, not as a separate figure. The modern split, which makes them rival categories, comes later.

Is a metaphor a type of analogy, then?

In modern usage, no. A metaphor is a figure of speech, an analogy is a comparison with reasoning, and most one-line metaphors do not state the reasoning that would make them an analogy. The two figures are siblings in modern handbooks: related, often deployed together, sometimes converging as a figure extends, but classified separately.

In the classical tradition, the categories overlapped. Aristotle's proportional metaphor is the case where analogy and metaphor are formally the same move. Scholars working in the classical frame still sometimes treat them this way; scholars working in the modern frame do not.

The classical position that a metaphor is itself a type of analogy holds on Aristotle's proportional case, and the modern position that it is not holds on the bare one-line metaphor that supplies no reasoning. Both positions are right about the case they describe.

The question for the writer in front of a draft is not which tradition is correct. It is which figure you are deploying, and that comes down to how much of the reasoning you want to put on the page versus ask the reader to supply. State the parallel and the reasoning, and you have written an analogy. Assert the identity and stop, and you have written a metaphor. The label follows the choice.