What is the paradox inherent in the title of the poem "The Canonization" by John Donne?

Let us remember that the speaker of this poem appears to
be addressing a cynic of love, who is arguing that the speaker's love for his beloved is
harmful or at least damaging to himself. Thus it is that the title of the poem refers to
the way that the speaker and his beloved can become "canonised" or be made saints
through the way that their love is expressed in poetry. Consider how the penultimate
stanza of this excellent poem explores the paradox between the actual nature of their
relationship and the way that it can be immortalised in
poetry:

We
can die by it, if not live by love, 
And if unfit for tomb or
hearse
Our legend be, it will be fit for verse ; 
And if no piece of
chronicle we prove, 
We'll build in sonnets pretty rooms ; 
As well
a well-wrought urn becomes
The greatest ashes, as half-acre
tombs, 
And by these hymns, all shall approve 
Us canonized for love
;

Even though the "legend" of
their lovemight be "unfit for tomb or hearse," it can be "fit for verse." Poetry seems
to be an apt way to give them the "canonisation" for the intensity of the love they bear
for one another, even though in life they may receive no recognition for it at all. The
paradox of the title refers to the difference between the way their love is thought of
by others and the way it can be immortalised in poetry. The fact that we continue to
talk about this poem so much nowadays gives testament to the way in which Donne achieved
the "canonisation" of the love between the speaker and his
beloved.