“Half the world’s population follows religions derived from Mosaic Law – that is, God’s commandments as communicated to Moses. Not surprisingly, given its vintage, Mosaic Law is obsessed with matters related to cleanliness and lifestyle factors that we now know play a key role in the spread of disease. Just as villages in the Fertile Crescent were giving rise to filthy, crowded cities, and outbreaks of illness were becoming an everyday horror, Mosaic Law decreed that Jewish priests should wash their hands – to this day, one of the most effective public-health measures known to science.
The Torah contains much more medical wisdom – not merely its famous admonishments to avoid eating pork (a source of trichinosis, a parasitic disease caused by a roundworm) and shellfish (filter feeders that concentrate contaminants), and to circumcise sons (bacteria can collect under the foreskin flap). Jews were instructed to bathe on the Sabbath (every Saturday); cover their wells (which kept out vermin and insects); engage in cleansing rituals if exposed to bodily fluids; quarantine people with leprosy and other skin diseases and, if infection persisted, burn that person’s clothes; bury the dead quickly before corpses decomposed; submerge dishes and eating utensils in boiling water after use; never consume the flesh of an animal that had died of natural causes (as it might have been felled by illness) or eat meat more than two days old (likely on the verge of turning rancid).
When it came time for divvying up the spoils of war, Jewish doctrine required any metal booty that could withstand intense heat – objects made of gold, silver, bronze or tin – to ‘be put through fire’ (sterilised by high temperatures). What could not endure fire was to be washed with ‘purifying water’: a mixture of water, ash and animal fat: an early soap recipe.
Equally prescient from the standpoint of modern disease control, Mosaic Law has numerous injunctions specifically related to sex. Parents were admonished not to allow their daughters to become prostitutes, and premarital sex, adultery, male homosexuality and bestiality were all discouraged, if not banned outright.
the use of disgust to punish people whose practices endangered the group could be leveraged to drum up moral outrage to condemn the cruel, the greedy and the malevolent
Religion is an ideal enforcer of good public health, for many of the behaviours most relevant to disease-propagation occur behind closed doors. There’s simply no way of getting around an omnipresent God ever on the lookout for those who defy His will. Lest His flock be tempted to stray from the fold, the Torah makes clear that there will be a steep health cost: the Lord will punish the disobedient with ‘severe burning fever’, ‘the boils of Egypt’, ‘with the scab, and with the itch’, ‘with madness and blindness’ – and, if all that fails, the sword.
The axiom ‘Cleanliness is next to godliness’ originated in Mosaic Law, and was subsequently embraced by Christianity and Islam. Hinduism evolved more independently, but is equally obsessed with bathing before prayer and concerned about contamination of the body and what parts should be allowed to touch other objects or people (the left hand, for example, is used strictly for bathroom functions, so it is a grave offence for a Hindu to offer food to someone with that hand).
Of course, the world’s great religions are about much more than hygiene. Indeed, they tend to be most preoccupied by matters related to spiritual purity, sacred duty and the preservation of the soul. But the use of disgust to punish people whose health practices endangered the group could easily be leveraged for the purpose of drumming up moral outrage to condemn the cruel, the greedy and the malevolent. This repurposing of the emotion gave society two benefits for the price of one as antisocial behaviour, like hygiene infractions, would be hard to police without the deterrent of an all-knowing God with a vengeful streak.