From an atheist background this is what made me want in * Philosophical arguments mainly from early medieval and Greek thinkers lead me to believe in the immortality of the soul, Natural law ethics (I don't think muslims believe in this), the existence of God, and some of his attributes (simplicity, there can only be one, essence is existence etc) * Researching the historical claims of the monotheistic religions I found that the resurrection stands above any others by far. This directly contradicts the Qur'an which makes the resurrection into a giant conspiracy story. Admittedly I really don't like the Qur'an though so I am a bit biased. * From then I went to research the conflicting theologies of the different denominations and I found myself believing that if Christ did found a Church on earth it was the Catholic Church. Coming from an atheist background I like to think myself mostly unbiased in my choice. Those are probably the main reasons. Apart from these there were maybe a couple of other things - I found myself changing my opinion on different things which I previously disagreed with the Church on (masturbation, fornication and divorce), I really like the Old Testament foreshadowing of Christ and the Gospel of John in particular and on top of that I think I've had a subtle calling to the Catholic Church and to religious faith in general.