Ever since Plato, philosophers have developed rational arguments for the existence of God. In the last decades the philosophical interest in these arguments has grown again significantly. In this book cosmological arguments are investigated. A cosmological argument derives the existence of God from the fact that there exist caused things. In the first part of this book the author argues that these arguments show that it is plausible that the cosmos was brought about by a necessarily existing conscious, free being. However, as is shown as well, it does not follow that this being is also the first cause of the whole of reality, something typically said of God. In the second part of the book a new argument for the existence of a first cause is presented, based on the premises of atomism and causalism. Subsequently, the author proposes a new modal-epistemic argument for the existence of a conscious, free being who is the first cause of reality. Objections to both new arguments are evaluated and refuted. The book concludes with the observation that these arguments can be combined with cosmological arguments in order to arrive at a renewed case for theism.