Lustrum of wild beasts, plural lustra ( ), a den of vice. Lustrum A lustrum (, plural lustra) was a term for a five-year period in Ancient Rome. The lustration was originally a sacrifice for expiation and purification offered by one of the censors in the name of the Roman people at the close of the taking of the census. The sacrifice was often in the form of an animal sacrifice, known as a suovetaurilia. These censuses were taken at five-year intervals, thus a lustrum came to refer to the five-year inter-census period. ' (from ', ) is a lustration or
How many angels can dance on the head of a pin? How many angels can dance on the head of a pin? The question "How many angels can dance on the head of a pin?" (alternatively ""How many angels can stand on the "point" of a pin?"") is a reductio ad absurdum of medieval scholasticism in general, and its angelology in particular, as represented by figures such as Duns Scotus and Thomas Aquinas. It is first recorded in the 17th century, in the context of Protestant apologetics. The question has also been linked to the fall of Constantinople, with the imagery of scholars debating about minutiae while the Turks besieged the