Activity in the part played by the individual's choice of a rule of life, by his seeking of solitude and shunning the world, is necessary for the first stages of the spiritual life, but it is of less importance in the soul's growth and formation than the purification which is brought about by God himself. As soon as the soul has begun to give herself generously to the work of her salvation, God begins to co-operate by sending her temptations or trials which show up the weaknesses and exercise the virtues which are most needed. We have called these trials passive because they are provided or allowed by God and the Christian does not have to choose the way to progress. But the will must choose to co-operate actively with God's grace in striving to master self and overcome the attack. In this way the first trials of the spiritual life require a great deal of activity and consequently are not technically Passive Purification in the sense generally accepted by spiritual writers.