Psychology is a broad field, but could be defined simply as ‘the study of human behavior and motivation.’ It became a scientific discipline a mere hundred years ago, but authors have been making psychological observations since the beginning of literature. The Bible, for example, though dealing primarily with our relationship to God, is often astute in its descriptions of human motivation. What is new with psychology is its strict focus on the topic. This focus distils and advances psychological insight, making it accessible to more people, like Christians who seek self-knowledge as a requisite for spiritual growth, “From self-knowledge, as from its source, proceeds the knowledge of God” (John of the Cross, Dark Night I.12). Psychology’s description of human behavior attains a clarity that can overcome our natural tendency to resist self-knowledge, to remain ‘blind’ or ‘defensive’ regarding our shortcomings. A dramatic example of psychological blindness is King David’s double sin of adultery and murder. When the prophet Nathan tells him about a rich man who for his own banquet prepared the beloved lamb of an impoverished neighbor, David condemns the rich man for his callous greed, “He deserves death!” David, however, does not recognize his own injustices until Nathan blatantly denounces him with, “That man is you!” (2 Sam 12:1-7). David’s rage is, for psychology, a ‘projection’ onto the rich man of David’s anger at his own sin. Scripture echoes the insight: “You judge, but do the very same things!” (Rom 2:1). With John of the Cross, then, let us strive daily for self-knowledge.