The Phrase Today
"Let there be light" is perhaps the most quoted sentence from the Bible. It functions in modern English as a declaration of creative power, the moment when something springs into existence from nothing. An architect unveiling a building design, a scientist announcing a breakthrough, a tech CEO launching a product -- all might invoke "let there be light" to frame their work as transformative. The phrase is athe motto of numerous universities (the University of California system uses "Fiat Lux," its Latin equivalent), libraries, and scientific institutions. It is used humorously (flipping a light switch) and seriously (inaugurating a new era). No other biblical phrase so concisely captures the idea of creation through spoken command.
Biblical Origin
The phrase appears in the third verse of the Bible, God's first recorded speech act:
> "And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness." (Genesis 1:3--4, KJV)
The Hebrew is yehi or (יְהִי אוֹר) -- just two words, among the shortest and most powerful sentences in ancient literature. Yehi is a jussive form of the verb "to be" (hayah), expressing a command or wish. Or means light. The sentence's power lies in its radical compression: the gap between command and fulfillment is zero. God speaks, and reality conforms.
Theologically, this verse establishes the doctrine of creatio ex nihilo (creation from nothing) and the concept that the divine word has creative power -- an idea that John's Gospel would later develop: "In the beginning was the Word" (John 1:1). The ancient Greek rhetorician Longinus, in his treatise On the Sublime (first century AD), cited this verse as the supreme example of the sublime style -- the most awe-inspiring sentence he knew.
How the KJV Cemented It
The Latin Vulgate's "fiat lux" had already made the phrase famous in educated European circles for over a millennium. Wycliffe's Bible (1380s) rendered it "Be maad liyt," which lacked the KJV's cadence. Tyndale (1530) wrote "Let there be lyghte," very close to the final form. The Geneva Bible (1560) used "Let there be light." The KJV's version is identical to the Geneva's, but the KJV's incomparably wider circulation -- as the standard Bible in every English-speaking church for centuries -- burned this sentence into the English-speaking world's collective memory. The monosyllabic simplicity of "Let there be light" -- five single-syllable words -- gives it an elemental force that perfectly mirrors the Hebrew original's brevity.
Semantic Drift
In Genesis, the light is the first act of cosmic creation, dispelling primordial chaos and darkness. It is God's light, not sunlight (the sun is not created until Genesis 1:16, three "days" later), suggesting something more fundamental than electromagnetic radiation -- a theological statement about divine order overcoming void.
In modern English, the phrase has been democratized. Anyone can say "let there be light" -- it has been detached from divine prerogative and applied to human creativity, scientific discovery, and even mundane tasks. The Enlightenment (itself a light-metaphor) adopted the phrase to describe the triumph of reason over superstition. Thomas Edison was frequently compared to God speaking light into existence. The phrase's journey from cosmogony to light-switch joke represents one of the most dramatic semantic descents in English.
Historical Usage
The phrase has been invoked at key historical moments. Benjamin Franklin's electrical experiments were described in "let there be light" language. The motto "Fiat Lux" was adopted by universities including UC Berkeley (1868), Clark University, and others, framing education as illumination. During World War II, the phrase appeared in propaganda about the coming victory of democracy over fascist darkness.
In science, the phrase has been adopted with particular enthusiasm by physicists. Paul Dirac's equation predicting antimatter was described as a "let there be light" moment. The discovery of the cosmic microwave background radiation -- the literal afterglow of the Big Bang -- was called the universe's "let there be light." The phrase bridges science and scripture in a way that few other biblical expressions can.
Cross-linguistic
The Latin "Fiat Lux" may be even more famous than the English version, thanks to its use in university mottos worldwide. German has "Es werde Licht" (Luther's translation), French says "Que la lumiere soit," Spanish uses "Hagase la luz." Every language with a Bible translation has its own version, and the phrase is recognizable across all of them. The two-word Hebrew original (yehi or) remains the most compact, and Hebrew speakers recognize it instantly. Arabic uses "kun fayakun" (Be, and it is) from the Quran (Surah 36:82) to express the same concept of divine creative speech, though the specific light-creation phrasing differs.
In Literature & Culture
Milton's Paradise Lost (1667) builds one of its most magnificent passages around this moment. Alexander Pope's epitaph for Isaac Newton plays on it: "Nature and nature's laws lay hid in night; / God said, Let Newton be! and all was light." The phrase appears in works by Goethe ("Mehr Licht!" -- "More light!" -- reportedly his last words), Tolkien (whose creation myth in The Silmarillion echoes Genesis 1), and countless others.
In film, the phrase structures the opening of 2001: A Space Odyssey (1968), where the dawn of intelligence is depicted as a light-moment. In popular music, it appears in songs by Metallica, Hillsong, and numerous others. The phrase is so foundational to Western culture that it functions as a kind of cultural Big Bang -- the first sentence of the story the West tells about itself.
Related Biblical Phrases
Genesis 1 produces several other enduring phrases: "In the beginning" (1:1), "without form and void" (1:2, sometimes rendered "formless and void"), "it was good" (1:4, 10, 12, 18, 21, 25, 31), "be fruitful and multiply" (1:28), and "have dominion" (1:28). John 1:1's "In the beginning was the Word" deliberately echoes Genesis 1, creating an intertextual chain. "The light of the world" (John 8:12) extends the light metaphor to Jesus himself.
Common Misconceptions
A common misconception is that the light in Genesis 1:3 refers to sunlight. The sun, moon, and stars are not created until Genesis 1:14--16, making the "light" of verse 3 a different phenomenon -- variously interpreted as divine radiance, cosmic order, or primordial energy. Another misconception is that "Fiat Lux" is the original phrase; it is the Latin Vulgate translation (fourth century AD) of the Hebrew. Finally, some assume the phrase is unique to the Judeo-Christian tradition, but creation-through-speech appears in Egyptian mythology (Ptah speaks the world into existence) and other ancient Near Eastern traditions, suggesting a shared cultural heritage that the biblical account transformed and made its own.