Summa Theologica is a comprehensive work of Christian theology written by Thomas Aquinas in the 13th century. It aims to explain the principles of faith and reason, addressing various theological questions and topics, including the nature of God, morality, and the purpose of human life. The text is structured in a question-and-answer format, making it accessible for readers. It is divided into three main parts, covering God, humanity, and Christ, and has had a significant influence on both theology and philosophy throughout history.