I am sorry if I gave you the idea I'm in the biz of redeeming reformed churches. 
And you're right, we are to work out our own salvation, and to examine ourselves.
(And the latter verse should also be taken in context. Believers shouldn't have to check every day to be sure they're saved, right?)
I don't see a mandate for examining the heart of another.
So I'd have to disagree that we ought to be 'making sure that all those who claim to be Christian are really in the faith'.
But if you know of scripture to support it, I'm open to learning. 
And whether we like it or not, we all come to God with a belief system.
It may not have a trendy label, but it's there.
We call it doctrine, and doctrine isn't evil.
Are you sure you are open to learning? Did Paul not say to the church at corinth to turn away the one who was in sin and in an incestuous relationship? there are many scriptures that talk about judgement starts at the church..so we have to be carefull to make sure we are who we say who we are..i say this not trying to be 'better' than you or anyone here, because i wish someone would have told me. But i had friends who because of their bad theological position thought God would always eternally secure them and their lives revealed the bad fruit of such wrong positions regarding God. Theology matters..a belief system matters..I never said it didn't..others here may avoid and run from any theological position in a vain attempt to 'keep the peace' but I never said i was against Doctrine..you must have confused me with some other folk here. If we are not as christians to be accountable and care for each other, then who else will? I am not saying I am to be a 'goat inspecter' and say i have the gift to separate the sheep from the goats! I am simply saying if i cannot tell my brother or sister to make sure they are serving God, then what on earth am i doing?! I say all this with conviction in my life because i had christian friends who at at time i was going south spiritually and for whatever reason they did not move a muscle to tell me hey, you are going the wrong direction! Come back! No..then again one of them, a calvinist told me he thought i was not a christian,(see the bad and erroneous position of a wrong theological stance and how it affects how you even treat others)
Regarding savedbygracesexibi's rant..I do not see how i could, as a 5 point calvinist if i was one, put any emphasis on living for God, I am merely taking what i have seen of calvinism and knowing that many calvinists do believe we christians are always wretched folk and hold onto eternal security too tightly aka what i like to call God's got you mentality. I would as many calvinists i met, be caught up with trying to be as worldy as possible yet still be considered christian, I would also embrace their antinomian ways(not saying all do) I most certainly would take five point calvinism to its logical conclusion by showing it in my life, by not loving others, looking down on the unsaved as reprobate filth(i know calvinists who do),call those who oppose me Goats,stupid,and sinners(ive had this happen to me) If i was a calvinist, i would not place much importance on my lifestyle and more on my election status or my self proclaimed election status.
But since Psychomom you think im talking craziness,give me some minutes to show that we as christians are to spur each other on, and if you find someone who is not living in him and he does not want to change...we are not even to talk to him, and throw him out of the church. I have no reason to make stuff up, but for your benefit and for the others, gimme a bit to look into exact verses so i am not accused of making this stuff up.
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regarding this part of your response----------------
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I am sorry if I gave you the idea I'm in the biz of redeeming reformed churches.
And you're right, we are to work out our own salvation, and to examine ourselves.
(And the latter verse should also be taken in context. Believers shouldn't have to check every day to be sure they're saved, right?)
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I think we should be checking every day..why would we not? Do you not want to make sure that everyday you are walking with God, and not take it for granted? And make sure that your heart is not deceiving you with a sinfull mindset? I surely wish i would have as a younger christian, but i also was going to a church that only appealed to the Love of God and Grace,which is good..yes, amen..there is grace and love but nobody ever told me how to respond to this grace and love with an application of Christian right living(of course enabled by God's spirit..if i was doing this on my own, well good luck with that Raul, tell me how it works out for you!) I can only go by own experience..i do not see i as checking every day that you are 'saved' persee, but since i do not hold onto eternal security of the P in Tulip or Tulip at all for that matter,and my view of eternal security is different..i call it, The Believer's security, so i do as of late check myself and my heart,and pray..God make me more holy, by your spirit..I want to be pleasing to you,and I want to be that beakon of Light that others see and point to as the one that showed them Christ. So I must graciously disagree, we should be living this 24/7, we cannot be skipping a day for the sake of 'grace' or worrying that we may be legalistic..this is not legalism. And this is from one who used to worry about being religious about not being religious..I was not living for God as I should have, but no one ever showed me either that this was possible, so many years later..I discovered a sweet spanish church that implements this, and does not tell me that i cannot keep my responsibility, as i have heard one Grace preacher say in a sermon here locally about a year ago..so, Now I finally know I can live a spirit Lead Holy Life.
