This is probably the best poem for "absence makes the heart grow fonder." The speaker of the poem is trying to "forbid" his lover from "mourning" the brief separation that is about to occur. He begins by suggesting that the separation need not be a dramatic event - they can accept it calmly, as it is not a matter of terrible fortune:
So let us melt, and make no noise,
No tear-floods, nor sigh-tempests move
The speaker then speaks of dramatic events of heaven, how large and momentous they are, but how "innocent" they are as well, because people on earth can not feel their effects:
But trepidation of the spheres,
Though greater far, is innocent
He moves on to the basis of his argument, the argument for why the two lovers should not mourn their time apart. His claim is that a parting between lovers is impossible (in a metaphysical sense). He suggests first that they share a soul, because both of their souls are made of the same material and so are the same. Therefore, by sharing a soul, they can not be divided:
Our two souls therefore, which are one,
Though I must go, endure not yet
A breach, but an expansion,
Like gold to airy thinness beat.
As seen above, their souls can not be separated but only expanded with the space that divides him. He moves on to argue that, if they do indeed have two separate souls, those souls are so interconnected that the same is true - they can never really be "apart." No matter where one of them goes, the other will be a foot that grounds the other soul in place so that it may return, as in a circle:
Such wilt thou be to me, who must,
Like th' other foot, obliquely run;
Thy firmness makes my circle just,
And makes me end where I begun.
It is a clever, spiritual argument to stop the sorrow of a separation, and is an excellent example of metaphysical poetry, which mixes the spiritual with the earthly in its expression.