From its origins in ancient India, where it flourished alongside Buddhism and early forms of Hinduism, Jainism has as its foremost principle "ahimsa," the non-harming of any living being. Ahimsa is connected to fascinating biological theories, in which the world is understood to be literally teeming with living souls. It's not only humans who have souls: so do animals, insects, and even invisible microbes present in all matter, including earth, fire, water, and air. Jains believe the principles of ahimsa extend even to these invisible microbes. They impose elaborate restrictions on their behavior to avoid harming even the slightest forms of life.
Jains are strict vegetarians who abstain from meat, fish, and eggs. They also avoid eating foods that involve destruction in their procurement, such as honey, which is believed to harm bees when it's harvested, and root vegetables, which involve undue digging and violence to the earth. Jains also avoid alcohol and other stimulating substances, because these are believed both to contain life and to weaken the resolve to practice austerity and ahimsa.
Jain restrictions are not only dietary. Jains try to curtail any activities that may be damaging to life forms. While lay people have some leeway, rules for monks and nuns are quite strict. They must avoid using electricity, machines, and vehicles (this means they can never travel overseas, and thus the Jain communities in the U.S. are composed only of laypeople). They drink water that is filtered so as not to consume and thus destroy life forms living in water. Sometimes they wear a cloth over their mouths to avoid breathing in small airborne creatures. One of the very few items they are permitted to use is a small whisk or broom for brushing the ground they walk on to gently sweep away small insects. For one school of Jainism, the Digambaras, the monks must refrain even from the use of clothing, since they are supposed to strive to be beyond all shame. The production and wearing of clothing is also perceived to be violent to tiny creatures.
For lay people, such strict rules are nearly impossible to follow. Instead, many of them practice ahimsa by promoting vegetarianism, supporting charitable activities both in India and abroad, and maintaining animal shelters.
While Jains are a tiny minority in India (less than 1% of the Indian population), their influence throughout history has far exceeded their numbers. Echoes of their uncompromising insistence on ahimsa may perhaps be felt in modern times when Dr. King says, in his "Letter from a Birmingham Jail," that the "question is not whether we will be extremist but what kind of extremist will we be. Will we be extremists for hate or will we be extremists for love?" For the Jains, whose call to nonviolence reaches beyond the concerns of human beings, no one can be too extreme or fastidious in caring for life.