Witnessing time's destruction of ancient monuments and the transience of states and kingdoms, the speaker reasons that time will inevitably take away his beloved, a thought that fills him with unresolvable grief.
Sonnet 64's eight-line meditation on ruin moves through multiple scales of destruction: individual monuments ('lofty towers'), metals thought eternal ('brass eternal'), territorial exchange (ocean vs. shore), and political kingdoms ('state it self confounded'). Each image is progressively more comprehensive—moving from the particular to the universal. The effect is accumulative dread. By the time the speaker reaches line 11, ruin has become not just a historical fact but an epistemological principle: it teaches. Ruin is the speaker's instructor in melancholy, transforming observation into prophecy. This cascade of images serves a psychological function: it justifies the leap from cosmic decay to personal loss as not illogical but inevitable.
The couplet ('This thought is as a death which cannot choose / But weep to have, that which it fears to lose') is philosophically complex. The thought of loss itself is death-like; moreover, the person who holds the beloved is caught in an unbearable paradox. To possess love is to be aware that possession is temporary. Weeping while holding the beloved is the accurate emotional response to this contradiction. The speaker cannot enjoy the beloved fully because consciousness of transience contaminates pleasure with dread. This is not romantic love but tragic awareness: love is inseparable from the fear of loss, and that fear is as real and present as the beloved themselves.
Like scrolling through news of collapsed civilizations or extinct species and thinking: 'If that can be destroyed, so can everything I love. Eventually I'll lose this person.' The sonnet captures how awareness of mortality in the world infects love with dread.