Father, Son (Jesus Christ), and Holy Spirit of Orthodoxy are not the same God as professed by the West.

Western Christian Theology...Roman Catholic and Protestant...leads to Atheism.

http://www.orthodoxpress.org/parish/river_of_fire.htm

Orthodoxy is the fullness of the faith...

Unaltered, died for by the Martyrs, defended by the faithful, preserved pure for over 2000 years.

Many have left it...of free will and choice...but that is not the same as saying it no longer exists.

That is not to say that an Orthodox cannot lose their salvation any more than those outside Orthodoxy are unsaved. But it is analogous to a person studying under a great mathematician...it neither guarantees they will become a great mathematician, but greatly increases their chances, nor does it mean that someone not studying under a great mathematician cannot become a great mathematician, but it does reduce their chances.