How many angels can dance on the head of a pin?
Thomas Aquinas's "Summa Theologica", written , includes discussion of several questions regarding angels such as, "Can several angels be in the same place?" However, the idea that such questions had a prominent place in medieval scholarship has been debated, and it has not been proven that this particular question was ever disputed. One theory is that it is an early modern fabrication, used to discredit scholastic philosophy at a time when it still played a significant role in university education. James Franklin has raised the scholarly issue, and mentions that there is a 17th-century reference in William Chillingworth's "Religion of Protestants" (1637), where he accuses unnamed scholastics of debating "whether a Million of Angels may not fit upon a Needle's point?"
This is earlier than a reference in the 1678 "The True Intellectual System Of The Universe" by Ralph Cudworth. Helen S. Lang, author of "Aristotle's Physics and its Medieval Varieties" (1992), says (p. 284):
Peter Harrison (2016) has suggested that the first reference to angels dancing on a needle's point occurs in an expository work by the English divine (minister), William Sclater (1575–1626). In "An exposition with notes upon the first Epistle to the Thessalonians" (1619), Sclater claimed that scholastic philosophers occupied themselves with such pointless questions as whether angels "did occupie a place; and so, whether many might be in one place at one time; and how many might sit on a Needles point; and six hundred such like needlesse points. "
Harrison proposes that the reason an English writer first introduced the "needle’s point" into a critique of medieval angelology is that it makes for a pun on "needless point". A letter written to "The Times" in 1975 identified a close parallel in a 14th-century mystical text, the "Swester Katrei". However, the reference is to souls sitting on a needle: "tusent selen siczen in dem himelrich uff einer nadel spicz" — "in heaven a thousand souls can sit on the point of a needle. "
Other possibilities are that it is a surviving parody or self-parody, or a training topic in debating. In Italian, French, Spanish and Portuguese, the conundrum of useless scholarly debates is linked to a similar question of whether angels are sexless or have a sex.
Origin
"How many angels can dance on the head of a pin?" It is first recorded in the 17th century, in the context of Protestant apologetics.