Insoluble

Insoluble (pronounced in-sol-yuh-buhl)

(1) A substance which cannot be dissolved, broken down or dispersed.

(2) That which cannot be solved; unsolvable; insolvable.

(3) That which cannot be explained; mysterious or inexplicable.

(4) In chemistry, a substance incapable of dissolving in a solvent.

1350-1400: From the Middle English insoluble (indestructible, unable to be loosened), from the Old French insoluble or the Latin insolūbilis (that which cannot be loosened), the construct being in (not) + solubilis (soluble) which replaced the Middle English insolible; Middle French borrowed the word from the Latin as insoluble.  In the sciences, the noun insolubility in the sense of “incapability of dissolving in a liquid” dates from 1754 (insoluble having conveyed that since 1713), the Late Latin insolubilitas having previously been used and from 1791 it replaced the Latin insolubilis (that cannot be loosened) although in the early seventeenth century it’d been used of the marriage vow to mean "that cannot be dissolved".  The curious (and in many way annoying as such thing in English are) parallel meaning "that which cannot be solved" dates from 1722 and etymologists think it likely a separate formation from the earlier senses.  The related adjective irresolvable was from the 1650s and was from an assimilated form of in- (not, opposite of), the meaning "that which cannot be resolved into parts" emerging after 1785.  Insoluble is a noun & adjective, insolubility is a noun and insolubly is an adverb; the noun plural is insolubles.

In chemistry, insoluble has the precise technical meaning “incapable of dissolving in a solvent” and while it’s actually rare for absolutely no solute to dissolve at all, many substances are poorly soluble although a compound may be insoluble in one solvent yet fully miscible in another.  There’s also the influence of external factors, most notable temperature; increasing temperature frequently improves the solubility of a solute.  The figurative sense (that which cannot be solved; unsolvable; insolvable) is actually used less than other words or phrases which convey the idea, doubtlessly because of the parallel meaning.  Some claim that in Medieval scholarship, it was a tacit conviction among the learned that the insoluble question did not exist and that all that was ever required was to find the right man whose studies were so deep that he would eventually deduce the answer.  It’s a modern-sounding idea and recalls some of the optimistic phases the United States went through in the twentieth century; probably few think like that now.

Dr Rowan Williams (b 1950; Archbishop of Canterbury, 2002-2012) and Benedict XVI (1927–2022; pope 2005-2013, pope emeritus 2013-2022), discussing insoluble problems during the papal visit to the UK, Lambeth Palace, London, September 2010

One who probably never felt quite like that but may at times have allowed himself the odd, brief moment of optimism was former Archbishop of Canterbury Dr Rowan Williams, a literary critic and one-time Professor of Divinity at Oxford although his decade in Lambeth Palace seems to have cured him of that.  In late 2008, Dr Williams took a two month summer sabbatical to finish a book about his literary hero, the Russian novelist Fyodor Dostoevsky (1821-1881) which was published as Dostoevsky: Language, Faith and Fiction.  Those few weeks may have been among the happiest of his life, later reflecting that “It was a wonderful experience actually, just being able to get up in the morning and write instead go to committees and answer letters and try to solve insoluble problems in the church.”  To the suggestion that prayer might provide answers to at least some of those insoluble problems he replied “I'll do just that.”  Ten years on, there little indication his prayers were answered.