Shakespeare’s speaker wonders how he could ever run out of material when his beloved is right there, breathing life into his verse. The beloved, he says, supplies a subject so excellent that ordinary paper can’t do it justice. If anything in the speaker’s writing is worth reading, the beloved should thank himself—because anyone, no matter how ineloquent, would find words when that same person sparks the light of invention. The beloved outshines the nine ancient Muses, and the speaker suggests he become the tenth Muse, ten times more valuable. Any poet who calls on him should produce timeless poetry that outlasts the ages. In the final couplet, the tone turns self-deprecating but still adoring: if these modest poems please the fickle readers of today, the labor belongs to the poet, but all the praise rightly goes to the beloved. The mood is one of intimate devotion and grateful wonder, as if the speaker is leaning close to say, You are my art’s only reason for being.
Sonnet 38: How can my muse want subject to invent — Summary
How can my muse want subject to invent, While thou dost breathe, that pour'st into my verse Thine own sweet argument, too excellent For every vulgar paper to rehearse? O! give thy self the thanks, if aught in me Worthy perusal stand against thy sight; For who's so dumb that cannot write to thee, When thou thy self dost give invention light? Be thou the tenth Muse, ten times more in worth Than those old nine which rhymers invocate; And he that calls on thee, let him bring forth Eternal numbers to outlive long date. If my slight muse do please these curious days, The pain be mine, but thine shall be the praise.