Derrida's différance describes how meaning is perpetually deferred through the infinite play of differences in language; undecidability refers to textual moments where meaning cannot be resolved into a single interpretation. These concepts challenge the assumption that texts have stable, decidable meanings.
Study Derrida's own readings of literary texts to see how deconstruction identifies undecidable moments that resist closure.
Derrida's most productive move is to take Saussure's insight — that linguistic signs have no positive content, only differential relationships — and push it to a destabilizing extreme. From your study of deconstruction and post-structuralism, you know that Saussure argued meaning arises from difference: "cat" means what it means not because it directly represents a furry animal but because it differs from "bat," "cot," "car," and every other word in the language. There is no natural bond between signifier and signified. Derrida accepts this but asks: if meaning depends on difference, and difference is relational, when does meaning ever arrive? Every sign refers to other signs, which refer to other signs — meaning is always ahead of us, deferred, never fully present. This perpetual deferral is what Derrida names différance.
The neologism is deliberate and untranslatable: in French, *différer* means both "to differ" (spatial) and "to defer" (temporal). Derrida's spelling with an *a* — *différance* instead of *différence* — cannot be heard in speech (both spellings sound identical in French), only seen in writing. This is itself a small demonstration of his point: the written mark registers a distinction that speech cannot capture, challenging the traditional philosophical privileging of speech over writing. Différance names both operations simultaneously — the spacing that differentiates signs from one another, and the temporal deferral by which meaning is always promised but never delivered as present, complete, and stable.
Undecidability follows from this structural deferral, but it is a more specific and textual claim. Derrida identifies moments in texts where a word or figure carries two incompatible meanings that cannot be resolved into a single interpretation — not because the reader is confused, but because the text structurally requires both. His reading of Plato's *Phaedrus* turns on the Greek word pharmakon, which means both poison and remedy. Plato's argument that writing is dangerous (a pharmakon) cannot be stabilized into one meaning: writing poisons memory but also preserves it; it is the cure for forgetting and the disease that causes it. The text cannot decide which it means, not because Plato was unclear, but because the word itself holds the contradiction. In Mallarmé, the word hymen means both the membrane (a veil, a boundary) and the consummation of marriage (its penetration, its disappearance) — simultaneously preservation and violation. Derrida argues these undecidable moments are not marginal curiosities; they are sites where texts reveal the instability beneath their apparent logical structure.
The crucial clarification against the common misconception: undecidability is not license for any reading. It is not the claim that "anything goes" or that all interpretations are equally valid. Derrida is identifying specific structural features of language — moments where the logic of the text cannot be resolved from within the text's own resources. This is a rigorous analytical claim, not a license for interpretive freedom. The undecidable reading must be demonstrated in the text; it cannot be invented. What deconstruction challenges is not interpretation itself but the assumption that a careful enough reading will always produce a stable, unified, fully present meaning — the assumption that language is more transparent than it is.
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