I once attended a "Faith Development". We started by observing a lighted candle, and were asked to write down any words that came into our heads. Some in the group put "Christian", "Jesus, the Light of the world! etc. The leader pointed out that it was simply a candle that had been lit. We ascribed Christian meanings to it, because of our experience as Christians. Faith, he said, could be about having faith that the sun would come up tomorrow!
Over the years there have been many who have tried to describe how we grow in faith, and have observed different stages that we go through. The most notable have probably been James Fowler and John H. Westerhoff III. There are of course critics of both their theories, but if you know nothing about them, you might enjoy looking up their work - be aware their American vocabulary can be difficult to understand.
Because much of the work on line is complex, I have paraphrased the thinking:
A description of Faith Development Stages (whether that a person is loved, or the sun will come up, or there is a God), might be described as:
Birth to around 2 years: Have some faith concerning loving parents/carers, and learning to trust, and love them. Cannot think in the abstract, and are unable to see the world from anyone else's perspective. Begin to get involved with their parent's rituals by experiencing them - whatever these rituals are (eg getting up in the morning, or going to church)
On average children of 6 to 12 years: Starting to see difference between facts, fantasy and speculation. Faith is experienced through story and ritual. Towards the end of this time beginning to see that others might have different beliefs.
Usually starts around age 13 years and can go on for all our life: Able to think abstractly, and see layers of meaning in stories, rituals and symbols, also see from others' perspectives. Can now claim their own faith, not just their family's faith. Religious authority is important.
This stage usually starts around 18-22 years, and involves questioning about their faith, beginning to reject some parts of their faith, while strengthening others to take greater ownership of their own faith journey.
Usually not gained until early 30s: The questioning begin to lead to a more comfortable place, where knowing all the answers may not be found. Accepting the importance of the whole community and their faith (eg we may not believe in every aspect of the Creed, but are happy that someone, somewhere, does!). Beginning to accept other faiths!
Few people reach this stage of faith: these people seem to have a simple faith that transcends all others, they have dropped the rules and regulations of faith and accept, for instance, that all they need is to know that "God is love". People like Mother Teresa or Gandhi might be such examples!