“fill'd with your most high deserts”
'Deserts' here means merits or what one is rightfully owed — the full worth that makes someone deserving of praise. The poet worries that even an accurate account of the youth's deserts will be dismissed as exaggeration.
“in fresh numbers number all your graces”
'Numbers' was the standard Elizabethan word for verses or metrical lines (counted feet), and the poet plays on both senses at once: to 'number' the youth's graces in 'numbers' is to count his qualities by writing poetry about them. This figure — using the same root word in two different senses in a single phrase — is called polyptoton.
- TLN 231historical topical
“The age to come would say 'This poet lies”
The poem stages a crisis of poetic credibility: future readers will call the poet a liar, because beauty this perfect sounds impossible. This is the central conceit of Sonnet 17 — the very accuracy of the poet's verse will condemn it as invention. The argument closes the first 17 sonnets' procreation sequence by showing that poetry alone cannot guarantee the youth's survival; a child is needed as living proof.
historical The procreation argument (Sonnets 1-17) “your true rights be term'd a poet's rage”
'Rage' here means poetic frenzy or inspired passion — the classical idea that poets write in a state of divine madness rather than cool reason. Used dismissively: future readers will say the poet's praise was just emotional excess, not sober truth. 'Your true rights' means what the youth genuinely deserves by right — his actual, owed praise.
“stretched metre of an antique song”
'Stretched metre' means exaggerated, overwrought verse — lines pulled beyond natural proportion to accommodate inflated praise. 'Antique' means old-fashioned, from an earlier era. Future readers will dismiss the sonnets as the padded verse of some forgotten, less reliable age — not as accurate contemporary testimony.