…the marriage of true minds (1)
The poet concisely defines his conception of ideal love as a bond between minds, not bodies or souls.
…love is not love which alters when it alteration finds, Or bends with the remover to remove. (2-4)
True love never changes or diminishes, despite any challenges it encounters. The confident certainty of "love is not love" shows us just how sure the poet is of his convictions, and this series of three repetitions emphasizes the negative definitions of love here – it doesn’t do any of these things.
O no! [Love] is an ever-fixed mark That looks on tempests and is never shaken (5)
Love is permanent and unchanging, even though adverse circumstances may arise; this is another sign that the love described here might be more of an ideal than a real-life experience. After all, what relationship can emerge from a huge fight totally unscathed?