The course aims to introduce the study of Christian prayer as the intimate and profound dialogue-communion relationship of the baptised person with God the Father, in Christ, in the Holy Spirit. Christian prayer will be analysed in its progressive and pedagogical development within the human-spiritual journey of the person, through the theological analysis of the book of the Interior Castle. This work, written by St Teresa of Avila, Doctor of the Church, masterfully describes the mystery of the union of the human being with the triune God and precisely explains the ways in which it is accomplished.