If the truth of Christianity (or any other religion) could be proven by logic, there would be no need for Faith. Faith is the foundation of religion not logic.
Christianity is a rational faith.
Philosophical thinking is what every mature, rational person does.
If you claim to embrace "the Christian faith", you surely realize that by merely making that claim, you are saying that you *know* what it is.
For instance ... I'm sure you know that certain essential (cardinal/core) doctrines are what make up the "Christian religion". What are they? And I'm also sure you know that if one steps outside those essentials of the faith and teaches or believes a different God and a different gospel, then that one is stepping outside the Christian faith.
That's fine. People do it all the time. The only time there is a problem with that is when they still think they can legitimately call what they believe "the Christian faith".