As if it weren't already clear, the poet writes that he has only one true love and that his poetry is only for the youth — the identical assertion presented in Sonnet 76. Just as the youth's beauty is immortal, so too is the poet's unchanging love for the youth: "Kind is my love to-day, to-morrow kind, / Still constant in a wondrous excellence."
Sonnet 105 repeats the contradictory idea that a "Fair, kind, and true" truth offers infinite scope for the poet's imagination. Only within the confines of a definite form does the imagination discover the meaning of infinity: "Fair, kind, and true have often lived alone, / Which three till now never kept seat in one" — in the young man. The youth's beauty is always the subject matter of the poet's verse, but there are infinite ways to express this beauty. However, whether the various means the poet employs truly express the youth's beauty is highly debatable.