In regards to how and one discerns true Christianity I am wondering how most of you folks do this because the vast majority of you folks from my understanding define a Christian in the sense of one that has faith in Jesus as the true and foretold messiah as well as the savior of mankind as well as someone who takes faith in the triune nature of the one true God. Now granted this would in and of itself would remove a boatload of religions within the scope of Christendom from even being possibly considered "true Christians" as certain sects such as Mormons, Jehovah's Witnesses, Christedelphians, 7th Day Adventists as well as certain Pentecostal groups. But the question that should be asked is (and I mean no intent of argument by this it is for the sake of dialogue) how is someone such as Joseph Smith or Charles Taze Russell any different from Martin Luther or John Calvin? All 4 of these folks brought a "new doctrinal understanding all together" to the people of Christendom which from as far as I know goes against the teachings of Jesus in Matthew 16 "For the gates of Hell shall not prevail"; on the same note it also begs the question why are groups such as Catholics and Orthodox Christians often lumped together with sects such as Mormons what is the reasoning behind this anyhow as there is no clear historical gap with either group and earlier Christianity in that sense as there is with the reformation or the restoration era nor do these groups deny the trinity or the validity of Christ's sacrifice and resurrection so not only am I wondering what is the reasoning behind why Catholicism or Eastern Orthodoxy is lumped in with Mormonism but why are they by many not even considered true Christians when they accept the basic definition of Christianity most western protestant churches teach which was stated earlier.