"People put up a version of Christianity suitable for a child of six and make that the object of their attack. When you try to explain the Christian doctrine as it is really held by an instructed adult, they then complain that you are making their heads turn round and that it is all too complicated and that if there really were a God they are sure He would have made "religion" simple, because simplicity is so beautiful, etc. You must be on your guard against these people for they will change their ground every minute and only waste your tune. Notice, too, their idea of God "making religion simple": as if "religion" were something God invented, and not His statement to us of certain quite unalterable facts about His own nature." -C.S. Lewis
As the band Caedmon's Call put it, "most things true are simple and complex." There may be simple things to grasp about God, but underneath there is always an ocean of complexity about Him. I often see atheists putting up straw man arguments of various watered down versions of Christianity. Many of them are eager to put forth apologists that say nonsensical things and call it Christian. Let us not do the same to them, but let us tackle the problems head on. The chief complaint of serious atheists is that there is not enough evidence. I understand that predicament and I don't think it's because they are mentally lacking as the above-mentioned nonsensical Christians will put it. I think the Bible speaks of an inner desire to run from God. Yet, for evidence, we can point to their conscience, the testimony of all creation's cohesion and complexity, the work of the Spirit in our lives, and most importantly the reliability of the New Testament's account of the death and resurrection of Jesus Christ. They might have their own criteria and will attack every one, but let those realities be the center of our conversation with the nonreligious.