“besiege thy brow, And dig deep trenches”
The poem opens with an extended military metaphor: winter weather attacks the youth's forehead as an army lays siege to a walled city, digging approach trenches ('trenches') to break down its defenses. The wrinkles of old age are those trenches cut into the 'field' of the face.
“Thy youth's proud livery so gazed on now, Will be a tatter'd weed”
'Livery' is a uniform or distinctive outfit worn to show membership in a great household — like servants' livery or a guild's dress; the youth's youthful appearance is the fine livery he wears now. 'Weed' is an old word for garment or clothing (not a plant), so 'a tatter'd weed' means a worn-out, threadbare garment of no worth — the same outfit in old age.
“all-eating shame, and thriftless praise”
'Thriftless' means wasteful, producing no return or profit — the opposite of thrift, which in Elizabethan English meant not just frugality but successful gain. To point at one's own sunken eyes as proof of beauty is 'thriftless praise' because it profits nothing: the beauty is spent, the account empty, and no child remains to make the claim credible.
historical The procreation argument (Sonnets 1-17)“'This fair child of mine Shall sum my count”
'Sum my count' is an accounting phrase: to sum an account is to add up the columns and strike the final balance. The child is the total that settles the ledger of the youth's life — proof that his beauty was not wasted but invested and returned with interest. 'Count' also carries the sense of reckoning or justification: the child is the answer when the youth is called to account for how he spent his gifts.
historical The procreation argument (Sonnets 1-17)“This were to be new made when thou art old, And see thy blood warm when thou feel'st it cold”
The closing couplet offers procreation as a form of resurrection: to have a child is to be remade at the very moment you feel most mortal. 'Blood' means both the literal warmth of life (youth's heat against the cold of age) and lineage or family descent — the child carries the parent's blood forward. The contrast of warm and cold in a single line is an antithesis that makes the argument sensory and immediate.
historical The procreation argument (Sonnets 1-17)