The wonder of natural philosophy in our 21st century, in the mind of the ordinary individual, has divided into political and humanist secular divisions. The widespread outlook of the Providence of God has been fragmented in our modern culture. St. Thomas Aquinas's synthesis on angels in the Middle Ages was not specifically a religious inquiry. It was also a study of natural philosophy. Angels are creatures whose existence can be demonstrated. In certain exceptional cases they have even been seen. To disregard them destroys the balance of the universe. 1 To include angels within the philosophy of nature of the cosmos today is to give a wider perspective to the articulation of the Providence of God in all its complexity. 2 We know from our personal experience that man is more than his body, because he has a power different from his physical body. This power is called intellect. Angels, created without bodies, are pure intellects. This fact with all its ramifications is the foundation for the Angel Institute Guide. It seems time to accept the existence of these intelligible beings we call angels as a vital aspect of our physical reality, natural philosophy and St. Thomas's Christian metaphysics. St. Thomas derived his information about angels from three sources. First, from astronomy which reached back to the ancient Greeks. Second, from the complex medieval history of metaphysics. Third, from the accounts of angels and demons in the Bible. 3 Etienne Gilson, a modern Thomist philosopher states: "The significance of the existential reform imposed by St. Thomas upon Greek metaphysics is one of the major events in the whole history of philosophy. If we do not grasp its meaning, we allow its fruits to perish." 4 This book discusses information we have from the Bible about the place and action of God's created beings, angels, in the physical universe. The Angel Guide gives a bird's eye view of the exceptional scholarly work available to us. A concise view of St. Augustine's work as well as St. Thomas Aquinas's, as it pertains to angels is provided. Information was extracted both from St. Thomas' own writing 'On The Angels' by the Dominicans publication, and from the reliable historical and philosophical work of Etienne Gilson, to whom I am greatly indebted. In the vast universe in which we as living individual human beings are a physical and immaterial part, the Angel Guide aims to expand our understanding of the Providence of God. The above ideas summarize the objective of the author in this very numinous and philosophically probing work on the Angels and their existence and relevance in the modern world and in God's universe.