Wiktionary
n. (context idiomatic often ironic English) That which is good, pure, pleasant, etc.
WordNet
n. a mild reasonableness; "when he learned who I was he became all sweetness and light"
Wikipedia
Sweetness and light is an English idiom that today is used in common speech, generally with mild irony, to describe insincere courtesy. For example: The two had been fighting for a month, but around others it was all sweetness and light. Originally, however, "sweetness and light" term had a special use in literary and cultural criticism to mean "pleasing and instructive", which in classical theory was considered to be the aim and justification of poetry.
Jonathan Swift first used the phrase in his mock-heroic prose satire, " The Battle of the Books" (1704), a defense of Classical learning (1704), which he published as a prolegomenon to his A Tale of a Tub. It gained widespread currency in the Victorian era, when English poet and essayist Matthew Arnold picked it up as the title of the first section of his 1869 book Culture and Anarchy: An Essay in Political and Social Criticism, where "sweetness and light" stands for beauty and intelligence, the two key components of an excellent culture.
Sweetness and Light is the second extended play by the English alternative rock band Lush. It was released on 15 October 1990 on 4AD. Featuring a less abrasive sound than the band's earlier releases, the title track was also released as Lush's first single and included the B-side "Breeze".
Tim Friese-Greene produced Sweetness and Light over a six-week period at the Greenhouse and Wessex Sound Studios in London. The recording sessions took considerably longer than Lush's previous sessions with Robin Guthrie and John Fryer, but resulted in a more atmospheric dream pop sound.
Sweetness and Light received mixed reviews upon release, but led to Lush's first major headlining national tour and placed in the national charts. The single was particularly successful in the United States, where it placed at No. 4 on the Billboard Modern Rock Tracks chart and received heavy rotation on radio.
Usage examples of "sweetness and light".
War is not sweetness and light, but the dirtiest thing in the world, and it is necessary to understand it as such and not to play at war.
Hence in writing up their experiences or, more usually, having a ghost do it for them they tend to gloss over their personality troubles, and so most written accounts of expeditions give a deceptive effect of sweetness and light.
As soon as she had a ring on her finger, she dropped the sweetness and light and turned into a harridan and as interesting and deep as the paint jobs they did on pickups.
All her talk of sweetness and light, all her memories of true love, all the lies she wanted us to believe: that she had been a virgin only twice removed before AM grabbed her and brought her down here with us.
But if we turn up at a rehearsal and cling to the walls, Geraint looks at us as if we were intruders, and the cast glare, or smile sweetly like old Twentyman, who seems to think it's his job to spread sweetness and light even in the humblest places.