"When I Consider How My Light is Spent" is one of the best known of the sonnets of John Milton (d. 1674). The last three lines (concluding with "They also serve who only stand and wait.") are particularly well known, although rarely quoted in context. Perhaps most known for quoting it is Hall of Fame baseball broadcaster Vin Scully, who would recite it when showing a player not in the game.
The sonnet was first published in Milton's 1673 Poems. In his autograph notebook (known as the "Trinity Manuscript" from its location in the Wren Library of Trinity College, Cambridge), Milton gave the sonnet the number 19, but in the published book it was numbered 16 (see Kelley, 1956; Revard, 2009, p. 569), so both numbers are in use for it. It is popularly given the title On His Blindness, but there is no evidence that Milton used this title; it was assigned a century later by Thomas Newton in his 1761 edition of Milton's poetry, as was commonly done at the time by editors of posthumous collections (Ferry, 1996, p. 18).
It is always assumed that the poem was written after the publication of Milton's 1645 Poems. It may have been written as early as 1652, although most scholars believe it was composed sometime between June and October 1655, when Milton's blindness was essentially complete. However, most discussions of the dating depend on the assumption that Newton's title reflects Milton's intentions, which may not be true. More reliable evidence of the date of the poem comes from the fact that it appears in the "Trinity Manuscript", which is believed to contain material written between about 1631 and 1659 (see Revard, 2009, p. 543); and that, unlike earlier material in the Trinity manuscript, it is not written in Milton's own handwriting, but that of a scribe, who also wrote out several other of the sonnets to which Milton assigned higher numbers (Shawcross, 1959).
Haskin (1994) discusses some of the likely interpretative errors that readers have made as a result of assuming that the common title of the poem is authentic. For example, the "one talent" that Milton mourns his inability to use is not necessarily his poetic ability; it might as easily be his ability to translate texts from foreign languages, the task for which he was responsible in the Commonwealth government. However, the references to light and darkness in the poem make it virtually certain that Milton's blindness was at least a secondary theme.
The sonnet is in the Petrarchan form, with the rhyme scheme a b b a a b b a c d e c d e, as can be seen in the text below.