What is Christian life? The answer to this question depends on how we understand Christianity itself. What does it mean to be a Christian? To profess some Christian religion? But there is no such religion. Jesus did not leave the world any religion. He left only a small community of His disciples, whom He Himself had brought into the life of the Kingdom. And He commanded them to continue what He had begun.
With His help and direct participation. All the religions that have grown on Christian soil are the work of human hands, and Paul understands this perfectly. Therefore he calls those to whom he addresses his letter not to despair while remaining in the good. Judging by the word the apostle uses, he is speaking not only of good works, of help to one's neighbor or something similar. He is speaking precisely of remaining in good, in the good. The corresponding Hebrew expression in Gospel times meant following the Torah and remaining on the path of righteousness.
Paul contrasts this state with what he calls vanity, or empty busyness, leading to nothing useful. Of course, empty busyness is harmful in every undertaking. But it is especially harmful on the Christian path, whatever that path may look like outwardly. For Christianity is not the ability to do something or not to do something. Christianity is the ability to be. To be in union with Christ. To live one life with Him, the life of the Kingdom He brought into the world. And to be the door through which the breath of the Kingdom enters this world, transforming it. Empty busyness is activity first of all.
Quite often it is simply unrestrained activism. And the point is not even that this activity is often quite meaningless. The point is the emphasis. The emphasis on doing something rather than on being. The attempt to replace one's true being and genuine existence with activity. This is always destructive, but especially in religious life: for the spiritual component in religious life is always much more clearly expressed than in any other form of life. And Christianity is not even religion, but simply spiritual life itself in its purest, unmixed form. The attempt here to substitute outward activity for being is the end of the path.
Although outwardly this path may seem to continue, and sometimes for quite a long time. Activity is always noticeable, it catches the eye, and the more of it there is, the deeper Christian life may seem to some observers in such an activist. Those who seek spiritual depth may seem to lose: in terms of outward, religious impressiveness they cannot compare with activists from Christianity. But the apostle calls such outwardly inconspicuous Christians, in terms of their activity, not to despair and not to lose heart: for they are occupied with the most important work of a Christian. They are learning to live in the Kingdom. Learning that without which there is no Christianity.