Write a critical note on John Donne's love poetry.

This is a fine question. Although John Donne's love poetry
is often read as if it is mostly secular (in other words, non-religious), a strong case
can be made that most of the love poems are fundamentally Christian in orientation. Some
of the poems (such as "The Good Morrow" or "A Valediction: Forbidding Mourning") seem to
teach Christian lessons fairly explicitly.  Others, however, such as "The Flea" or "To
His Mistress: Going to Bed," can be seen as teaching Christian lessons through ironic
implication.  In other words, some of the love poems seem to celebrate genuinely
unselfish, spiritual love of another person by showing such love openly.  Other poems,
conversely, imply the value of unselfish, spiritual love by showing the absence of such
love.

In Donne's day, Christians (who made up the vast
majority of the population) were expected to love God first and foremost.  If they loved
God properly, they would also automatically love everyone and everything else in the
universe properly.  However, if they loved themselves first and foremost (and were thus
guilty of the chief Christian sin of pride), they could never love anyone else or
anything else in the proper way.  Genuine love of others rooted in love of God was
called caritas (charity) and was the ideal kind of love.  False
love of others rooted in love of self was called cupiditas
(cupidity) and was associated with selfish desire and often with mere
physical lust.

Thus it is possible to argue that the
speakers of "The Flea" and of "To His Mistress: Going to Bed" do not truly love the
women they desire; instead, they merely feel selfish physical lust for those women.  By
mocking such lust through the irony of his poems, Donne (one can argue) actually
endorses its opposite, the true spiritual, Godly love known as
caritas. In some poems, however, such as "A Valediction: Forbidding
Mourning," Donne openly celebrates caritas. He thereby makes clear
the positive standard against which he judges the shortcomings of the lust mocked in
poems such as "The Flea."