Late antique and medieval cultures were preoccupied with cleanliness. Everything they held dear was susceptible to corruption, a concern that weighed heavily on the minds of contemporary writers. Early Christians were driven to produce a response to Jewish and pagan perspectives on the question of purity and pollution very early on. As Muslims advanced into Christian lands, they too came into contact with competing notions of purity and pollution and were made to respond.

Views on purity and pollution reflected a wide range of cultural preoccupations and have been employed to effect profound social changes in Late Antiquity and the Middle Ages. The concept of pollution is therefore a useful lens with which to observe late antique and medieval societies, whose most central convictions were often anchored to the complementary concepts of purity and impurity. For Christian communities, the liturgical year divided time by alternating between sacred and profane. Jewish and Islamic dietary laws restricted the body’s access to nourishment by forbidding certain foods and drinks, regulating the production of permitted food, and controlling bodily purification cycles. In Christianity, access to the shrines of saints and to their relics was gained only after a meticulous process of physical and emotional cleansing. Similarly, handling a Torah or a Qur’an were actions that had clear consequences in terms of purity and pollution. 

The pure/impure dichotomy is pervasive in contemporary compositions, from all fields of knowledge. Medicinal texts were aimed at restoring balance to the ailing body and expelling contaminants. This was also a prevalent motif of thaumaturgically themed episodes in hagiographies, which depicted the discharges and convulsions of the impure body healed by the presence of the saint. Heresiological and theological texts defined the boundaries of Christian orthodoxy and orthopraxy, condemning divergent expressions of the faith as agents of contamination. The detailed discussions of hypothetical ablution scenarios in Islamic ṭahāra legislation reflect a similar concern. 

The objective of the research group is to investigate how the concept of pollution was understood and applied by late antique and medieval authors, with a focus on the period spanning from the fourth to the thirteenth centuries, in all regions in which Jews, Christians, and Muslims wrote during this chronological timeframe. Thematically, it is interested in expressions of pollution in such areas as dogma, diet, medicine, sexuality, law, and violence.

Yaniv Fox: Featured Fellow>

The phenomenon of "warning colours" in poisonous insects, reptiles, and plants is one of the examples that can be used to demonstrate how biology and game theory can interact. Poisonous animals and plants are well known for their conspicuous contrasting colours. This is interpreted as the signal that indicates "I am poisonous, don't eat me". The question is, can we trust this signal? Biologists have studied this topic for decades, attempting to explain why "cheaters" -- non-poisonous animals with conspicuous colours -- are rare. This question will be tackled from a different standpoint, where perhaps the conspicuous animal does not warn its predator, but rather signals it to "come and inspect me". Other investigations will deal with mechanisms that can explain patterns of morphology, systematical and also behavioural, by using game-theoretic models.