3 ideas
The soul is a single crystal castle with seven sets of rooms arranged in concentric rings, and God lives at the center. The outer three dwellings are reached through human effort in prayer, self-knowledge, and ordered living. The inner four are given rather than earned: recollection, the prayer of quiet, union, spiritual betrothal, and finally spiritual marriage, in which the soul and God stay joined the way rain merges with a river.
Teresa says the only entrance to the castle is prayer and reflection, meaning attention to whom you are speaking and what you are asking. Many people live their whole lives in the outer courtyard among the 'reptiles' of worldly distraction without knowing they have an interior at all. Self-knowledge and knowledge of God are not separate projects, because a person comes to understand themselves only by looking toward the one who dwells at the center.
Visions, locutions, and consolations are not evidence of progress in themselves, because they can come from imagination, melancholy, or deception. The test is what they leave behind: real encounters with God produce humility, peace, stronger love of neighbor, and readiness for hardship, while false ones leave the person agitated, proud, or self-absorbed. Teresa therefore puts ordinary charity and good works above extraordinary states as the measure of union.