So long as men can breathe,or eyes can see; So long lives this.explain!

These are the concluding lines of “Sonnet-XVIII" composed by William Shakespeare, the famous dramatist and poet of the Elizabethan period. These lines suggest the immortality of the fair youth as well as the pride and confidence of the speaker. 

In these lines the speaker has rounded up what he has said in the other twelve lines of the poem. The beauty of the fair youth is better than that of a summer's day for several reasons. Rough winds blow and destroy the blooming roses in summer. It is short and its temperature changes frequently. Not only a day in summer but also all the beautiful things of nature are subject to mutability. But the beauty of the friend is not subject to any change or destruction. it is permanent and everlasting. It is made immortal by the power of poetry. As long as human beings will be on earth, and as long as they will read this poem, the friend’s beauty will be remembered and he will continue to live in the hearts of the readers. 

Thus, in these lines the enmity of time and the law of mutability have been defeated and the beauty of the friend has been immortalised. These lines also reflect the pride and confidence of the speaker for his capability of making his friend immortal. The speaker’s boasting of his capability seems to be peculiar but it was the tradition of the Elizabethan period.