Definition of "quiddity"

A tub of butter, contemplated by him, amounts to a Platonic idea. He understands a leg of mutton in its quiddity. He stands wondering, amid the commonplace materials of life, like primæval man, with the sun and stars about him.

October 1822, Charles Lamb, “The Old Actors”, in London Magazine‎, Mr. Munden

My vision reeked with truth. It had the tone,The quiddity and quaintness of its ownReality.

1962, Vladimir Nabokov, Pale Fire

He represented my quiddity I suppose – the part which, thanks to you, has converted a black pessimism about life into a belief in cosmic absurdity.

1978, Lawrence Durrell, Livia (Avignon Quintet), Faber & Faber, published 1992, page 352

When I send a card, it has to be right. Something that sums up the essential quiddity of being me, right here, right now.

2023 December 8, The Big Issue, Melbourne, page 35, column 1

They have ſwallowed and digeſted all the Fathers, the Codes, Provincials, Decretals, Pandects, Councils, Canons ; are Maſters of all the Schoolmen, not to fill their Heads and ſtuff their Writings with Quiddities and Quoddities, and far-fetched unintelligible Diſtinctions, but to be able to reaſon cloſely, to argue ſolidly, to rebuke, to confute, to reply, to rejoind, to ſyllogize, to criticize, to apologize, to advertize, to ſermonize, to decypherize, to――

1744, A Dialogue Between the Rev. Mr. Jenkin Evans and Mr. Peter Dobson, concerning Bishops.‎, London: M. Cooper, at the Globe in Pater-noſter-row, page 37