The earliest British evidence for this use of ‘suppositum’ is from c1428 — or is it? The Word-List gives ‘sopositus’ as a variant from 1374, which would constitute a significant antedating. Here's the slip:
This differs from our other quotations in several ways: it's spelt ‘sop-’ rather than ‘supp-’; it's masculine rather than neuter; and it goes with the name of a town rather than an institution. Besides, I don't believe Oxford has ever called its members ‘supposita’. So I decided to have a closer look.
The quotation is taken from Reginald Poole's 1890 edition of John Wyclif's De dominio divino (c1374). Here's the context:
Nec credo mentem cuiusquam ad tantum desipere quod credat divinitatem moveri in acquirendo dominium; cum stat Petrum ex pacto per … mortem patris … acquirere … dominium, sine motu per talis dominii acquisicionem … materialiter introducto: ut, posito quod Petrus existens Oxonie sopositus pepigit cum Paulo parente Rome quod post B instans habebit C thezaurum, sicut successione hereditaria habebit immobilia Pauli patris; tunc Paulo defuncto pro B instanti acquiret ad tantam distanciam ignoranter dominium, sine hoc quod proporcionaliter moveatur.
Nor do I believe that anyone's mind is so foolish as to believe that divinity is changed in acquiring dominion, since it is possible for Peter, by means of an agreement, to acquire dominion through the death of his father with no change being materially introduced by the acquisition of such dominion – as, supposing that Peter, being sopositus at Oxford, has agreed with his father Paul at Rome that after time B he will have treasure C (just as by hereditary succession he will have the immovable property of his father Paul), then with Paul dead at time B he will at such a distance unwittingly acquire dominion, without being changed correspondingly.Note that, dialectically speaking, Wyclif doesn't need Peter to be a member of the university; his being in Oxford is just a device to prevent the transfer of dominion from Paul in Rome from having any intrinsic effect on him. (Ironically, philosophers will recognize it as a mere Cambridge change.)
Moreover, Poole's glossary entry for ‘sopositus’ – ‘a subordinate member, as of a university’ – was qualified with a caveat: ‘if the reading be correct’. One of the three manuscripts he used for his edition had ‘sopo'us’; the others had ‘sopo'tus’, as does the MS from which they may derive:
The hunt is on, then, for alternative ways of expanding the abbreviation ‘sopo'tus’. A search for ‘sopo-’ across six of Wyclif's works yields five other hits, all beginning with ‘sopor-’, so how about ‘soporatus’ (having fallen asleep)? This would give the phrases in bold in the above passage as:
Petrus existens Oxonie soporatus … acquiret ad tantam distanciam ignoranter dominium
Peter, being asleep at Oxford, … will at such a distance unwittingly acquire dominionI think this works nicely, with ‘Oxonie’ accounting for the ‘ad tantam distanciam’ and with ‘soporatus’ hammering home the ‘ignoranter’. It would be nice to have some corroboration, though, e.g. from mentions of sleep in other 14th-century discussions of extrinsic change. Meanwhile, the new fascicule of the DMLBS (SOL–SYR) errs on the side of caution: