That I actually have read and formally studied the Christian Bible, Biblical history, Christian theology, and Christian apologetics, and that I have had plenty of the same experiences of the Holy Spirit or answered prayers that they have.
That I'm also aware of the supposed archaeological evidence such as the "shroud of Turin," as well as numerous supposed instances of miracles such as the Fatima sun dance and "scientific" claims about quantum brains, souls, the Cognitive-Theoretic Model of the Universe, the fundamental arguments for God (such as the ontological, deontological, cosmological, fine-tuning, beauty, and apparent design arguments), etc.
That I actually have read Tertullian, Justin Martyr, Augustine, Kant, Kierkegaard and so on. I'm even familiar with Rastafarian and Rosicrucian beliefs, including "Christian Cabala" and other forms of Christian mysticism and Christian esotericism.
That it's my familiarity with Christian mysticism, Christian existentialism, and Jeffersonianism that allows me to accept that there can be a rational basis for being a Christian in a religious sense. The issue is the claims of miracles, the resurrection, prophets, and the afterlife, as well as with those who believe in God as some sort of concrete being who exists in reality rather than a philosophical concept.