By their fruits you shall know them.

"Beware of false prophets, who come to you in the clothing of sheep, but inwardly they are ravening wolves. By their fruits you shall know them. Do men gather grapes of thorns, or figs of thistles? Even so every good tree bringeth forth good fruit, and the evil tree bringeth forth evil fruit. A good tree cannot bring forth evil fruit, neither can an evil tree bring forth good fruit. Every tree that bringeth not forth good fruit, shall be cut down, and shall be cast into the fire. Wherefore by their fruits you shall know them."
Matthew 7:16-20

The only really effective apologia for Christianity comes down to two arguments, namely, the saints the Church has produced and the art which has grown in her womb.
Cardinal Ratzinger, The Ratzinger Report

One of the really effective critiques of Christianity has to be that of Friedrich Nietzsche. Like any effective challenge, it doesn't underestimate the power of its opponent. Nietzsche knew that Christianity was mythos as well as logos. Jonathan Macintosh, on his blog The Flame Imperishable, writes,

"In The Birth of Tragedy from the Spirit of Music, an early work that ended his career as a philologist while confirming his calling as a philosopher, Nietzsche argues that the fundamental being of things, so far from constituting a universal harmony, instead embodies an original, violent, and terrifying discord and chaos, one that the Greeks symbolized (Nietzsche argues) through the originally Asiatic god Dionysus. Pitted against the annihilating abyss underlying reality, human existence and experience are a “terror and horror,” an ultimate futility and suffering in which consolation may nevertheless be found through a heroic effort of self-assertion and the artistic creation of meaning, value, and order."

Nietzsche rejects the view of the cosmos as fundamentally ordered and harmonious, and instead claims that existence is futile - any meaning is imposed by humans. So against Ratzinger's art and saints we have Nietzsche's modernist solution - the ubermensch and his self-assertion. The choice is an aesthetic one because it comes down to whether we view chaos or cosmos as primary.

My own choice is clearly with cosmos - ie. order and harmony. A pagan friend said to me "The experience of obedience is not central to one's experience of the universe." The problem with the pantheist viewpoint is that given that our experience of the universe is ambivalent - sometimes we suffer, sometimes we thrive - and given that the universe is all there is - there is no reason to see the world as of any inherent value or goodness in itself. It is something terrible, implacable, to be feared and propitiated, as the animists do. Or it is something pitiless which we have ultimately to extricate ourselves from, as in the aim of much Hinduism, Buddhism or Gnosticism. But it is not a gift of a good God, an overflowing act of generosity, to which the proper response is indeed praise and thanksgiving, and ultimately obedience.

Ratzinger is right to see this theistic and Christian viewpoint as producing the strongest apologia - art and the saints. Time and again, the view of the redeemability of suffering, the belief in the eucatastrophe - the sudden happy turn when all seems lost, provides us with strong foundations to bear good fruit. And the encounter with Christ, in whom all of God's generosity comes to meet us, is a fountain of living water that springs up eternally within us, enabling the poorest and most broken to be the inheritors of the Kingdom.