In a comment I was asked if I had read "What Makes You Not a Buddhist"? by Dzongsar. I will read it (because it looks good) but in the mean time I got some of it off the web here. Although I'm not sure all Buddhists would agree with this it seems right to me. Basically, according to this, you are a Buddhist if you believe in the 4 seals, which are (1) all compound things are impermanent, (2) all emotions are pain, (3) all things have no inherent existence, and (4) Nirvana is beyond all concepts. As Dzongsar notes, the comprehension of the 4 seals is the tea, everything else: the practices, the rituals, etc., are the cup. However, it is important to note that the terms used in the 4 seals are translated and do not have exactly the same meaning as the english words used in translation. For example the (Tibetan) Buddhist concept of emotion is very different from what we normally mean by emotion in the west (e.g., see Emotional Awareness: Overcoming the Obstacles to Psychological Balance and Compassion by Paul Ekman and the Dalai Lama). I'll try to post some more on this issue, but properly understood I don't think holding any of these beliefs precludes being a Christian. In fact, the metaphor of the tea and the cup is very helpful in understanding how someone can be a Buddhist Christian. If we think of a chalice for the Christian religion then we can see that the same substance can be held by a cup or a chalice. The cup and the chalice are there to hold a substance and allow us to drink it in. Being a Buddhist Christian means understanding that the cup and chalice contain the same thing.