How many angels can dance on the head of a pin?


"How many angels can dance on the head of a pin?" is a reductio ad absurdum challenge to 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. It also has been linked to the fall of Constantinople, with the imagery of scholars debating while the Turks besieged the city.
In modern usage, the term has lost its theological context and is used as a metaphor for wasting time debating topics of no practical value, or questions whose answers hold no intellectual consequence, while more urgent concerns accumulate.

Origin

'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 proved 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, 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, says :
Peter Harrison has suggested that the first reference to angels dancing on a needle's point occurs in an expository work by the English divine, William Sclater.
In An exposition with notes upon the first Epistle to the Thessalonians, 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 clever 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:
Other possibilities are that it is a surviving parody or self-parody, or a training topic in debating.
In Italian, Spanish and Portuguese, the conundrum of useless scholarly debates is linked to a similar question of whether angels are sexless or have a sex.