A courtier of King Charles I, Lovelace, this Cavalier poet, wrote this famous and oft quoted stanza describing what can not bind freedom and offering an analogy showing what can experience freedom the way he experiences it, the way he knows it. In order to understand the fourth stanza, we have to see it in relationship to the others.

The first three stanzas describe three instances when Lovelace knows unbounded freedom. This is a freedom, a "liberty," that is not rivaled by the freedom of gods of the air,  not known by fish in the deep sea, not felt by storm winds that toss the sea waves.

The Gods that wanton in the Air,
   Know no such Liberty.
[...]
Fishes that tipple in the Deep
   Know no such Liberty.
[...]
Enlargèd Winds, that curl the Flood,
   Know no such Liberty.

The fourth stanza turns and gives the paradoxical counterpoint to the three stanzas going before. In the fourth, instead of saying where he knows and experiences freedom and liberty, as before, Lovelace says, instead, what he will not recognize as a prison; what he will not recognize as a captivity that subdues and robs his liberty.

Lovelace famously says that walls do not rob freedom, do not rob liberty; that iron bars do not bind liberty; and that innocent minds are not harmed by walls and bars. He then summarizes the meaning of the first three stanzas and states that (1) innocence sees imprisoning chains and bars as a religious "Hermitage," a place where divine love is contemplated; (2) that he has freedom in the love he speaks of; (3) that in his hermitage of iron and stone, his soul is free.

The ending analogy states that only Angels "that soar" in the heavens, far above mortal walls and iron bars, know the freedom and liberty he knows. The fourth stanza thus speaks of true liberty and gives comfort to Lovelace's beloved from whom he is separated.

Stone Walls do not a Prison make,
   Nor Iron bars a Cage;
Minds innocent and quiet take
   That for an Hermitage.
If I have freedom in my Love,
   And in my soul am free,
Angels alone that soar above,
   Enjoy such Liberty.