Logic
Logic enters English in the late fourteenth century from Old French *logique*, itself from Latin *logica*, borrowed from Greek *logikē* (τέχνη), meaning 'the logical art' or 'the art of reasoning.' The Greek adjective *logikós* derives from *lógos* (λόγος) — a word of such systemic density that any single translation falsifies it. *Lógos* means simultaneously: word, reason, speech, account, proportion, discourse, argument. This ambiguity is not a defect in the Greek system; it is the system.
The PIE Foundation
The root is Proto-Indo-European *\*leǵ-*, which carried the meaning 'to collect, gather, choose.' From this same root come Latin *legere* ('to read, gather'), *lex* ('law'), *electio* ('selection'), and *legatio* ('embassy, delegation'). The English cognate *lecture* shares this ancestry, as does *collect*, *elect*, *select*, *neglect*, and *legend* (literally 'that which is to be read').
The semantic movement from *\*leǵ-* ('to gather') to *lógos* ('reason, word') is paradigmatic of how language encodes the architecture of thought: gathering — selecting — ordering — articulating. These are not separate activities. They are one activity viewed from successive positions within the system.
The Greek *lógos*
Among the pre-Socratic philosophers, *lógos* designated the principle of rational order underlying all phenomena. Heraclitus (c. 500 BCE) used it to name the universal law governing change. In Aristotle's *Organon* (c. 350 BCE), *logikē* became a formal discipline — the study of valid inference — and the word began its narrowing from a cosmic principle to a technical term.
This narrowing is a structural event. The word entered a specialized subsystem of philosophical vocabulary and lost its connection to the broader field of *lógos* as 'speech' and 'word.' What had been a word about the whole relationship between language and reality became a word about a particular procedure within that relationship.
The Latin Transmission
Roman writers latinized *logica* directly from the Greek but held a certain suspicion of the word's foreignness. Cicero sometimes preferred *ratio* or *dialectica* — the latter from Greek *dialektikē*, from *dialogos* ('conversation'), itself from *lógos*. Boethius (early sixth century CE) established Latin translations of Aristotle's logical works that would dominate European education for nearly a millennium, cementing *logica* in the curriculum of the seven liberal arts, where it sat alongside *grammatica* and *rhetorica* in the *trivium*.
The three arts of the trivium are not accidental companions. Grammar studies how words are structured. Rhetoric studies how words persuade. Logic studies how words *entail*. All three are, in the deepest sense, arts of *lógos*.
Into Medieval French and English
Old French *logique* is attested from the twelfth century, and Middle English *logik* appears in texts from approximately 1380, including Chaucer. The word entered through the university system — Paris and Oxford were transmitting Aristotelian scholasticism, and *logica* was its foundational instrument. The medieval logicians expanded the discipline considerably: modal logic, the logic of terms, *suppositio* theory. The word's range of application grew even as its technical precision increased.
Cognates and the Extended Family
The *lógos* family in English is striking in its breadth. Every word ending in *-logy* ('the study of') is a direct sibling: *biology*, *theology*, *psychology*, *etymology* itself. The suffix *-logy* comes from *-logia*, from *lógos* in its sense of 'account, discourse.' To study etymology is literally to give an account of true meanings (*étymos*, 'true' + *lógos*).
Further cousins include *analogy* (proportion between proportions), *prologue* (speech before), *epilogue* (speech after), *catalogue* (a gathering-down, from *kata-* + *légein*), *dialogue*, *monologue*, and *eulogy* (good speech). *Logarithm* — coined by John Napier in 1614 — combines *lógos* with *arithmós* ('number'), meaning 'ratio-number.'
Through Latin *legere*: *lecture*, *legend*, *legible*, *elect*, *select*, *collect*, *neglect*, *diligent* (from *diligere*, to single out with care), *intelligent* (from *inter-legere*, to choose between), and *religion* (etymology disputed, but one strong case connects it to a *leg-* root in the sense of binding obligations together).
Semantic Drift and Modern Usage
In contemporary usage, *logic* oscillates between its technical sense (formal systems of inference, symbolic logic, mathematical logic) and a looser vernacular sense meaning something like 'internal coherence' or 'rational justification' — as in 'the logic of the market' or 'I don't follow your logic.'
This vernacular use is a partial return toward the older *lógos* — the word is again being used to describe structural principles in systems, not merely the mechanics of syllogism. The digital age has added another layer: Boolean logic, logical gates, logical operators. Here *logic* names the binary arithmetic of decision, as far from Greek cosmology as one can travel — yet still operating within the grammar of *\*leǵ-*: gathering, selecting, ordering.
The word has traveled from a PIE root meaning to gather, through a Greek noun that meant the whole relation between mind and world, through Latin scholasticism, through medieval universities, into a modern English term that can describe both the most rigorous formal systems humans have devised and the informal reasoning of everyday speech. The distance is vast. The connection is exact.