“The question PetroniusMaximus is asking is how do I really know that I’m saved if I don’t know that, in the very end, I will persevere-like your Buddhist friend. I would suggest there are tests for us to see if we are in the faith (2 Cor 13:5-8) the most important is scripture and an active prayer life.”
I think you make a valid point. In the parable of the sower, sometimes the seed never takes root. Sometimes the soil is shallow, so the plant cannot last. That sounds like my Buddhist friend...who was only a Buddhist for about a year until he switched to something else. Sometimes the seed is choked by the weeds...sounds like the plant is alive, but not healthy. But maybe not. And then there is the seed that grows and bears fruit.
So time plus a hunger for God’s word and desire to speak with him would all be pretty strong signs, to which I would add the fruit of the Spirit. If God has been in you for many years, you will know. For my part, I suppose it took 20 years or more before I started to realize God wasn’t letting go, and to trust that he would really see me through to the finish.
It is a bit odd - the longer I go, the more I realize I don’t deserve anything, and the more certain I am that God has given me everything I need.
This I think is an indication of spiritual growth. Throughout my life I have had peaks and valleys like everyone else, but it always is God that keeps pushing me on. And the farther I go, the more I see what a wretched creature that I am and just how much God has more work to do in me. This is not false humility but simply an honest and objective appraisal of my current condition.
Like you, I have had some very dear friends leave the faith. As the Baptist Confession tells us, you really can never be certain about anyone's elses faith except your own. This is simply because you know what your own personal relationship to God is. You cannot possibly know what someone elses relationship is. As the Baptist Confession teaches us, we rest upon God's promises and His Spirit bears witness to our Spirit to humble us to submit to His reign and rule.
I will add an addemdum here. While one may know the status of their relationship before God, that is the ONLY relationship one can know. Thus, people who we may think are great Christians may turn out at some point not to be. This could be a friend, it could be a pastor, it could be the Pope. This is often how heresy gets introduced. We cannot judge others (unless they are committing eggregious sin) but we should be cautious in promoting people. Likewise, people who we may think are very luke warm may be used down the road by God in a mighty way. We cannot judge others; either one way or the other. We can only judge ourselves.
Here is an interesting sermon on the The Parable of the Sower. I like it because the fruit we exhibit are the fruit of the Holy Spirit. Do you have joy? Do you have peace? Are you more loving? Can you truthfully say this is God working in you to help mold you into a better person? These are the promises of God and the evidence of the Spirit working in us, to the praise of His everlasting glory.