In the old age black was not counted fair,
Or if it were, it bore not beauty's name;
But now is black beauty's successive heir,
And beauty slandered with a bastard shame:
For since each hand hath put on Nature's power,
Fairing the foul with Art's false borrowed face,
Sweet beauty hath no name, no holy bower,
But is profaned, if not lives in disgrace.
In the second  quatrain  Shakespeare introduces the recurring theme in the sonnet sequence; the personification of Nature, which bestows beauty on humans in general in, for example  Sonnet 11 , and the “fair youth” specifically, for example  Sonnet 20 . Nature’s power has been usurped by cosmetics, allowing a wearer with no  true beauty  to appear attractive. 
 A similar tension between false and true beauty is discussed in  Sonnet 67  as an insult to Nature. She is also personified in  Sonnet 68  and  Sonnet 126 .
Sonnet 127