Owen is writing about the central ideas in "Sonnet 18” by William Shakespeare. But thy eternal summer shall not fade,
Nor lose possession of that fair thou ow'st,
Nor shall death brag thou wander'st in his shade,
When in eternal lines to time thou grow'st,
So long as men can breathe or eyes can see,
So long lives this, and this gives life to thee.

What is the central idea of these lines?

The author’s loved one will overcome physical death and summer is eternal.
Attraction, love, and mild summer days are all fleeting and soon disappear.
Beauty is not defined by the outward appearance, but by the character inside.
The author’s loved one will always remain beautiful in the lines of this poem.