Initial consideration

     When giving consideration to any particular set of beliefs, the first place to start is it's internal consistency.  In other words, are the claims and/or beliefs of the religious system consistent with one another.   If at one point, belief system X says that "a" is true, then at another point says that "a" is not true or that "b" contradicts "a" to some degree, the system is internally inconsistent.  If a religious system is flawed at such a fundamental level, then continued investigation at deeper levels is pointless.
     Practically speaking, being able to comprehend, interact with and analyze a set of beliefs is vital.  The less clearly and articulately one is able to think, the more likely one will be deceived.  

The Christian faith, as taught and practiced by the Orthodox Church, is the only belief system that will pass an articulate critical analysis.  In other words, at some level, all other belief systems or religions will fail.  The Orthodox faith is the only faith that flawlessly answers all criticisms.
     Of course, not all other belief will fail such a critical internal analysis.  There is further investigation that can be pursued that will reveal other fallacies.  Even if a belief system is internally consistent, it could hold false presuppositions.  Ultimately, there will be some belief that is faulty.  This has to be the case.  If one starts from a foundational question and works upward, answering each question correctly, one will end up at the Orthodox faith.  If one does not, then one has answered something wrong, somewhere along the line.

     Of course, there is always the point of personal lack of understanding or wisdom.  No one person is ever perfectly clear in his thinking.  We can be deceived.  We can make logical or emotional errors.  This is one reason that we look to the early church fathers for guidance.  When we can look to the wisdom of the church, as guided by the Holy Spirit, we can be assured of our position in the faith.