Jains affirm a strict vegetarianism that goes further than most, extending non-harm to the smallest forms of life. Devout Jains avoid not only meat, fish, and eggs but also root vegetables such as potatoes, onions, and garlic, because uprooting the plant kills it and because roots are held to harbour innumerable minute one-sensed beings (and, in traditional understanding, colonies of subtle organisms called nigodas). Many also filter water, avoid eating after dark to prevent harming insects, and restrict foods thought to contain or breed many lives.
The classification underlying this practice traces to Umasvati's Tattvartha Sutra, the earliest systematic exposition of Jain doctrine, accepted as authoritative by both Digambara and Svetambara Jains despite their other disagreements, probably composed sometime between the second and fifth centuries CE. It sets out the taxonomy of beings by the number of senses they possess, from one-sensed life in earth, water, fire, air, and plants up to five-sensed animals and humans, and treats even one-sensed beings as possessing life (jiva) whose harm generates karmic consequence, the philosophical basis teachers of the tradition cite when explaining why root vegetables, understood to harbor concentrated one-sensed and nigoda life, are avoided even though such caution goes well beyond what most other vegetarian traditions in India observe.