Allan Kardec. The book of spirits (№ 395675)

Question: since spirits can't improve otherwise, how enduring the vicissitudes of bodily existence, does it not follow from this that the material life is some kind of test or purgatory, through which the beings of the spiritual world, to achieve excellence?
Answer: Yes, it is. They improved in these trials, avoiding evil and practicing goodness. But only after many incarnations, after a longer or shorter time, depending on their efforts, they reach the goal of perfection to strive for.