In one of our recent philosophy colloquiums, Fr. James Lehrberger presented a rather interesting discussion of the 19th century German philosopher, Nietzsche, and his critique of Christianity. I've heard plenty about the guy before, but not his specific argument against the faith.
Basically, Fr. Lehrberger allowed Christian doctrine to provide its own answer to Nietzsche's accusation that it is a religion fueled by an unconscious envy, hatred, and spirit of revenge. This answer is quite useful for what it attempts to disprove (namely that vengeance and hatred are at the heart of Christian doctrine). However, it does not attempt to address the fundamental discord between Nietzsche's philosophy and the tenets of Christianity, the fact that each simultaneously claims to be the only true path to human fulfillment. Nietzsche's assertion that Christianity consciously celebrates weakness and subservience and rejoices in the destruction of the strong was shown by Fr. Lehrberger's argument to be inaccurate: Christianity claims with every bit as much confidence as Nietzsche to the the route to a fuller and more glorious humanity. This nonetheless leaves us, however, with two radically opposed pictures of what it means to be human, each of which alleges that the other will in practice destroy everything dynamic and noble in a man.
For Nietzsche, the ultimate human good is the advantage of the individual. Christian emphasis on a person's duties towards others seems to him no more than an attempt of the weak to depict standards protecting their kind from robbery, murder, tyranny, or other "crimes" as based upon some objective moral standard. Only the weak and vulnerable benefit from commandments and laws forbidding violence or trickery, while those who are strong and intelligent enough to use such means for their gain are penalized. The greatest human good is realized in whatever person is most independent of such effeminate myths, most free to use his natural advantages to his own benefit, and most rich in those advantages which allow him to retain this independence unchallenged.
A very different conception of what it means to be human drives the message of Christianity. Man is not brought to perfection but in fact is dehumanized when he isolates himself from his fellow men and acts in a manner that puts him into constant competition with them. To be human is to be an intrinsically relational being. Whatever actions harm one's fellow men harm oneself as well, and true humanity therefore necessarily excludes whatever actions violate the standards of just interaction between human beings. Conversely, actions which benefit the weak benefit also the actor, as in strengthening one member of the Body of Christ, they bring a more perfect life to all.
Essentially the question that one who examines Nietzsche's critique carefully must ultimately face is whether his proposal or the Church's message promises true human fulfillment. An adequate answer would fill a book at least, but it is true that to some extent, the latter option makes more intuitive sense. As we live our lives, it's hard to make the case that we are most complete as lone individuals seem very convincing at all to ourselves. The principle of rationality really does appear in our daily lives as a concrete reality, and it is from this experiential base that we can be motivated to help defend the Christian view of man's meaning in life.