Which ethical rules are binding for a lay person? And what about alcohol, meat and vegetarianism?

The Vinaya prescribes no disciplinary penalty for a lay person who breaks these rules (secular law is a separate matter). The five rules / precepts (pañcasīla) are a training (pañca sikkhāpadāni): tasks a person takes on voluntarily. AN 8.39 calls these five precepts great gifts: whoever keeps them gives limitless beings freedom from fear and hostility and gains a share in that freedom themselves.

The canonical five precepts are abstention from:

• killing living beings (pāṇātipātā veramaṇī);
• taking what is not given (adinnādānā veramaṇī);
• unwholesome sexual conduct (kāmesu micchācārā veramaṇī);
• false speech (musāvādā veramaṇī);
• intoxicating drinks that are a ground for heedlessness (surāmerayamajjapamādaṭṭhānā veramaṇī).

On uposatha days a lay person may take eight precepts for a day and a night (AN 8.41), including complete abstention from sex for that period. Such a temporary vow lets lay people get a better feel for how monks live, and further purifies the mind.

Sex. Unlike monks, lay people are not bound by a vow of celibacy. The third precept only requires avoiding (see MN 41) relations with women protected by mother, father, brother, sister, relatives or the Dhamma, women who are betrothed or married, and those with whom a relationship breaks the law.

Alcohol. Surā, meraya and majja are names of intoxicating drinks mentioned in ancient Indian texts; extending the rule to modern substances is reasonable, but the Pali formula contains no literal list of them. What is meant is complete abstention: intoxication weakens mindfulness, and with it the ability to keep the other precepts. DN 31 lists six everyday consequences of addiction to intoxicants: loss of money, quarrels, illness, a bad reputation, indecent exposure, weakened wisdom.

Meat. The early texts prescribe no general vegetarianism. MN 55 sets out the threefold rule, binding on monks who receive almsfood: meat may not be eaten if you have

• seen,
• heard,
• or suspect

that the animal was killed specifically for you. The Vinaya relates that one of Devadatta’s main demands was precisely to make five ascetic points compulsory for monks, including lifelong abstention from fish and meat; the Buddha refused and confirmed the allowance of meat pure by the three conditions (Kd 17). Killing itself and the meat trade are, of course, forbidden to monks and considered undesirable for lay people (see AN 5.177, MN 55).

Where to read: AN 8.39, MN 41, MN 55.