The study of the science of Apologetics is very necessary in these days of doubt and agnosticism. The fundamental principles which underlie all religious belief are daily called in question. And even if the urgent need of a reasoned grasp of the foundations of Faith did not exist, the interest of the subject of Apologetics, the large outlook upon life which it involves, the coherence of its parts and the cogency of its conclusions make it desirable that an examination into the principles of Theism should be an indispensable adjunct of Christian teaching.The first step to take in the investigation of the claims of Natural Religion is to prove that an objective world exists, a world external to consciousness. The ground for this belief must be examined so as to justify the transit from consciousness to reality. In the process, one begins to realise, perhaps for the first time, the truth that there arc many characteristics of the external world which our perceptive faculties are not keen enough to observe. At the same time, it can be shown that our perceptions, though not adequate, are true as far as they go, and this conclusion is sufficient for the validity of the well-known argument that contingent beings postulate the existence of a First Cause upon whom all contingent existences depend, the necessary personal Being, to whom we give the name of God. God exists. Man has been created by God. Man has been endowed with a spiritual soul-spiritual because for its existence and action it is independent of matter, and therefore persists after the death of the body. Man owes to God the debt of private and public acknowledgment and worship. Here in brief arc the main theses of Natural Religion. Supported by this basis of Natural Religion, and aided by the application of the criteria of mirarlcs and prophecy, the enquirer is led to the further conclusion that there is one and only one true form of Supernatural Revelation, namely Christianity. In the following chapters an attempt has been made to reproduce in English form the classical argument.... which are set forth in text-books of Apologetics written chiefly in Latin, French and German. The aim has been to avoid as far as possible technical nomenclature, so that Senior Students of Secondary Schools may follow the trend of the discussion. If such students are called upon to unravel the intricacies of the Differential and Integral Calculus set for B.A. and B.Sc. degrees, it is surely not too much to expect that the metaphysical principles which arc the support of Natural and Supernatural Religion should have some share of their attention.In the development of the Apologetic argument, I desire to acknowledge my indebtedness to the Dominican work Pere Garrigou-Lagrange's "Dieu, son existence et sa Nature."