Augustine (rightly) says that both the beginning of end of faith is a gift of God, both the initial belief and the perseverance to the end (Rebuke and Grace, and Perseverance). As Paul says, “I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ” (Phil 1:6).
But this “fact” does not reduce human experience to nothing. We know that people profess faith, have “initial enthusiasm” as Paul Carter recently noted. And this initial enthusiasm often wanes, and so does one’s professed faith. There is no reason to deny this regular experience because the Bible affirms that he who began a good work in us will bring it to completion.
I find this to be one of the oddest things people do: oppose experience to faith as if they contradict each other.
What happens here is that someone finds an initial benefit in Christianity, and so professes a faith which is both shallow and enthusiastic. We all know someone who gets excited about one thing after and another. This week it’s baking, the next week it’s knitting, the week after it’s powerlifting.
This is the kind of thing that happens. And after all, Christianity is attractive because it’s good; and goodness draws people to it since we were created for goodness. Yet apart from seeking that goodness in and through Jesus Christ, we will have no stability—no long term perseverance.
Since, and this is really important, perseverance means persevering in FAITH. That is a gift of God (Eph 2), not something naturally producible.
All that to say, we should not oppose experience to faith, since the same God who gifts faith to us made the universe for us to experience. One God, one reality.
This does not mean our experience is always reliable. But it can be reliable.