The paradox that ends Sir Henry Wotton's "The Character of a Happy Life" represents the culminating idea of the entire poem: that people don't need a lot to have everything.
The five stanzas leading up to this statement establish the narrator's perspective regarding what is and is not essential in life. Stanza one focuses on independence, praising those "[t]hat serveth not another's will" and are honest. Stanza two establishes the importance of those who pursue their own passions rather than the passions of others, and praises those "[u]ntied unto the world by care / Of public fame or private breath." In other words: those who do not act in the name of a legacy or their own selfish gain.
Stanza three focuses on the importance of not being envious, of staying away from vices, and of living not by "rules of state, but rules of good." Next, stanza four discusses the importance of consciousness and staying away from rumors and gossip. Stanza five establishes the importance of religious worship and of the grace, rather than the gifts, of God.
Through all these stanzas, the narrator presents a list of things not to have. One should not be tied to the will or passions of another, should not have fame or selfish desires, should not have envy, should not deal in rumors, and should not want gifts from God. In this way, one shouldn't have anything superficial. Yet by not having or desiring any of these things, one would have grace, a moral code, free will, freedom from materialism, and a free mind. Therefore they could be seen as "having nothing" of little importance, yet having all of utmost importance.