“wherefore with infection should he live”
'Infection' means moral corruption or contamination, not physical disease. The poet asks why the youth should live alongside a world diseased by sin — as if mere proximity to vice might taint genuine virtue.
“lace itself with his society”
'Lace' here means to adorn or trim — as lace was stitched onto clothing to embellish it. Sin borrows the youth's company to dress itself up and appear respectable. 'Society' means companionship or association, not a social organization.
“steel dead seeming of his living hue”
'Steel' means to fix or confirm — to make as hard and permanent as steel. 'Dead seeming' means a lifeless appearance or imitation. 'Hue' means complexion or color. The line says: why should false cosmetics work to confirm and preserve a dead copy of the youth's living complexion?
“Nature bankrupt is, Beggar'd of blood to blush through lively veins”
Lines 9-12 build an extended financial conceit: Nature has gone bankrupt — exhausted her treasury of genuine beauty — and now survives on the youth's credit. 'Beggar'd of blood' means stripped of the vital blood that made real color in living cheeks. 'Exchequer' (line 11) is the royal treasury; 'lives upon his gains' means Nature draws her income entirely from the youth's surplus. The conceit maps economics onto beauty: the youth is Nature's only remaining asset.
historical The sonnet form