While few contemporary critics interpret Shakespeare's sonnets as "personal allegory," asserting that speculation about what the personal implications of Shakespeare's life, morals, and sexuality is an exercise in futility. Nevertheless, since there is always something of the artist in his art, certain sonnets give evidence of elements of subjectivity; that is, seemingly personal addresses and personal expressions of feeling.
Taken as a whole, the sonnets of Shakespeare trace the speaker's growth in love. First, he praises his friend for his beauty in Sonnet XVIII; however, there is also jealousy and disappointment expressed, and never is the young man who is addressed physically described in detail. The only suggestive evidence of a real young man is Shakespeare's inscription in one edition to "Mr. W. H." [possibly William Herbert, the Earl of Pembroke, or (with the WH initial order reversed) Henry Wrothesley, the Earl of Southhampton. Cruiously, the relatioship changes after sonnet XVII and becomes more erotic in subsequent ones of the first section. However, if the reader follows the growth of love in the sonnets as defined in Dr. Erich Fromm's The Art of Loving, the childish adoration and jealous feelings give way to prepubescent conflicts of homoeroticism that are exhibited in Sonnet XX.
Then, as the young man normally matures, he turns his love to a lady in Sonnets CXXVII-CLIV. Here the speaker's love is at first infatuation which turns erotic and then spiritual and unselfish. Again, the identity of this "Dark Lady" is speculative, at best with several ladies of Queen Elizabeth's court as possibilities. Finally, in Sonnet CLI, the speaker observes,
Love is too young to know what conscience is.
Yet who knows not, conscience is born of love?
Clearly, then, Shakespeare's speaker believes in some ultimate quality of pure love and being; that is, "the art of loving." Interpreted as a study of love and its growth, there is, then, a personal involvement by Shakespeare in his sonnets and, certainly, a subjective element as he measures this growth through his perspectives on two of his beloved.
Additional source: The Art of Loving by Erich Fromm: Harper & Row.