A lot of people say that they believe in God. This was used as a measure in some churches, at one point, to indicate if a person is a christian or not. There is a slight problem with using this as a measure.
James 2:19 You believe that there is one God. Good! Even the demons believe that—and shudder.
The bible says demons believe in God and tremble. So believing in God does not necessarily mean you are a christian. There must be a better way to determine if a person is a christian or not. I wonder if it has less to do with an outward act or performance but an inward transformation.
Only God in a persons life can produce the God fruit that only God can bring. Someone can change their life, habits and speech. They can do this for a moment or a set period of time. Some can change their actions on a permanent basis but only God can change the heart and establish his kingdom in a person. This cannot be faked. Only God can produce this level of change. So the test is not if you believe in God but more-so has God transformed your heart? If this is the case then your life will flow with a power that only God can produce.
We are meant to become what we believe. Not our effort but his handiwork. Believing in God is the foundation for experiencing God.