«Full many a glorious morning have I seen
Flatter the mountain-tops with sovereign eye».
Sonnet 33 begins a new phase in the poet and youth’s estrangement from each other. (The breach well may be caused by the youth’s seduction of the poet’s mistress, which the poet addresses in later sonnets.) In any case, faith between the two men is broken during the poet’s absence.
Full many a glorious morning have I seen
Shifts in the poet’s attitudes toward the youth and about his own involvement in the relationship are evident in the sonnet. Whereas in Sonnet 25 the poet boasts that his faith is permanent, here he reverses himself. References to “basest clouds,” “ugly rack,” “stealing,” “disgrace,” and “stain” indicate that the friend has committed a serious moral offense. Whereas in earlier sonnets the poet worried that his verse was not good enough to convey his intense love for the young man, now he worries about whether the young man is as good as his verse conveyed. Metaphorically, the young man is like the sun, which “with golden face” warms and brightens the earth.
However, the sun allows “the basest clouds” to block its rays, and the young man permits loyalties to other people to interfere with his relationship with the poet. The poet accepts that the friend has betrayed him — “But, out alack, he was but one hour mine” — but he also realizes that the burden of blame must be his own for having assumed that outward beauty corresponds to inner virtue. This last realization, that outward beauty does not correspond to inner virtue, is expressed in the sonnet’s last line: “Suns of the world may stain when heaven’s sun staineth.” In other words, “Suns of the world may stain” — perhaps a pun on “sons” or humankind — represents the young man’s moral transgression although his external, physical appearance remains unchanged. Nevertheless, the poet’s love for the young man remains unchanged.
English audio from YouTube Channel Socratica
Summary from Cliffsnotes.com