St Teresa begins to talk about another grace than the prayer of meditation. Meditation seeks to think much about God, to use the understanding, in order to awaken the will to devotion. But what happens when love begins to dominate prayer? What happens when a loving knowledge enters the soul without long processes of thinking? The Fourth Mansions are dealing with this supernatural prayer, the infusion of divine contemplation. In this prayer, in order to keep ascending, "the important thing is not to think much, but to love much." She urges us to do that which most leads to love.
In this passage, St Teresa gives a wonderful description of the signs of charity, divine love. Charity makes us want to please God in everything, in no way to offend Him. Charity makes us pray for the honour and glory of His Son and the growth of the Catholic Church. Apostolic fruitfulness especially begins as God awakens this higher love in us.