A collection of ~40 short natural-science puzzles (why does seawater not nourish trees? why do bees hate smoke?) each answered with several rival explanations, none endorsed.
Quaestiones Naturales ("Natural Questions") is one of the shorter essays in Plutarch's Moralia, the huge miscellany of ethical, scientific, and antiquarian writing that survives alongside his famous biographies. It is built entirely from a single recurring formula: a question about the natural world is posed, and then two, three, or four possible causes are offered in succession, introduced by "Is it because..." or "Or is it rather that..." Plutarch almost never picks a winner; the essay is a display of the range of Greek scientific opinion rather than a settled treatise.
The topics range widely across botany, zoology, meteorology, and oceanography: why seawater does not nourish land plants, why rain nourishes seeds better than irrigated water, why herdsmen give livestock salt to lick, why octopuses and chameleons change color, why she-wolves all give birth within the same twelve days, why bears rarely gnaw through hunting nets, why bees cannot endure smoke, and why water looks white at the surface but black at the bottom. Plutarch draws on named predecessors throughout — Aristotle, Theophrastus, Empedocles, Plato, Democritus, Anaxagoras — quoting or paraphrasing their explanations and sometimes testing them against counter-examples from his own observation (marsh reeds that fail to grow without seasonal rain, water-clocks that run slower in winter, the physician Mnesitheus's clinical observations about food cravings in pneumonia patients).
The work matters less as a store of correct answers — many explanations rest on now-discarded physics of hot/cold/dry/moist qualities — than as evidence of how educated Greeks under the Roman Empire practiced natural inquiry: by cataloguing competing hypotheses from the philosophical schools rather than performing decisive experiments. It also preserves quotations from lost or fragmentary poets and thinkers (Empedocles, Alcman, Theognis, Aratus) that survive nowhere else, making it a minor but genuine source for the history of early Greek natural philosophy.
“Why does seawater not nourish trees? Is it for the same reason that it does not nourish land animals either?”
— Quaestiones Naturales · read this chapter →
“you could not step twice into the same rivers”
— Quaestiones Naturales · read this chapter →
“Why can bees not endure smoke? Because the passages of their vital breath are extremely narrow, and this breath, intercepted and shut in by the smoke, chokes them and drives the bees nearly to death.”
— Quaestiones Naturales · read this chapter →
“Why does the octopus change its color? Is it, as Theophrastus thought, that it is by nature a timid creature, so that when disturbed it turns with its breath and changes color along with it, just as a person does”
— Quaestiones Naturales · read this chapter →
“Why do animals, when they fall into some affliction, seek out and pursue the remedies that help them, and often benefit from using them — just as dogs eat grass in order to vomit up bile”
— Quaestiones Naturales · read this chapter →
It is a short essay from the Moralia consisting of dozens of natural-science questions — about plants, animals, weather, and the sea — each followed by two or more possible explanations that Plutarch does not resolve. It reads like a catalog of rival theories from Greek philosophy rather than a systematic scientific treatise.
Rarely with a single answer. His standard method is to offer one explanation, then introduce alternatives with phrases like 'Or is it rather that...', leaving the reader with a menu of live hypotheses drawn from different philosophical schools.
He names and quotes Aristotle, Theophrastus, Empedocles, Plato, Democritus, Anaxagoras, and poets including Homer, Heraclitus (via quotation), Alcman, Theognis, and Aratus, using their views as competing explanations for natural phenomena.
Plutarch reports the belief that bees are fastidiously clean and keenly sensitive to smell, so they detect and attack people who have recently committed adultery more readily than others; he illustrates this with a jesting line from Theocritus about Venus being stung for her affair with Anchises.
He lists several examples — dogs eating grass to induce vomiting, pigs eating river-crabs against headache, the tortoise eating marjoram after viper flesh, bears eating ants when nauseated — and debates whether this is guided by instinctive scent-recognition or by bodily cravings produced by illness, comparing it to pregnancy cravings and a physician's clinical observations.
By modern standards, no — its explanations rely on ancient qualitative physics (heat, cold, wetness, dryness) rather than empirical testing. Its value today is historical: it shows how educated Greco-Roman readers organized natural curiosity and preserves quotations from otherwise lost early Greek writers.
Moralia: Ad Principem Ineruditum · Moralia: Adversus Colotem · Moralia: Amatoriae Narrationes · Moralia: Amatorius · Moralia: An Recte Dictum Sit Latenter Esse Vivendum · Moralia: An Seni Respublica Gerenda Sit · Moralia: An Virtus Doceri Possit · Moralia: An Vitiositas Ad Infelicitatem Sufficia · Moralia: Animine An Corporis Affectiones Sint Piores · Moralia: Apophthegmata Laconica · Moralia: Aquane An Ignis Sit Utilior · Moralia: Bruta Animalia Ratione Uti