There are many arguments for and against the use of CAS. This book sets out to provide an argumentative case for the use of CAS. The first section outlines some of the key issues surrounding the use of CAS and the related research, which supports these findings. The next section details the ideas of teachers from various countries who already use CAS in teaching learning and assessment. It sets out their experiences in terms of lesson ideas, teaching sessions, and the adaptations which have to be made to question types and examination papers, to assess suitably. The final section of the book outlines the arguments for and against the use of CAS (“the Advocatus Diaboli”), providing what the authors believe is a convincing case for the use of CAS in the teaching and learning of Mathematics.