In recent years , Alister McGrath has gained prominence as one of evangeli calism's preeminent theologians . A brilliant scholar and communicator , he combines the clarity of thought of a scientist ( he holds a Ph.D. in molecular biology ) with the deep convictions of a committed Christian and theologian . Studies in Doctrine contains four of McGrath's more popular theological works : • Understanding Doctrine explains what doctrine is , why it is important , and what its limitations are . • Understanding the Trinity moves from a superb apologetic for God's existence , to developing a concept of God , to a probing and balanced examination of the Trinity proper . • Understanding Jesus is a basic , eminently readable , and surprisingly personal introduction to the person and work of Christ . Justification by Faith demonstrates how the vitality and relevance of the doctrine of justification by faith can be recovered and presented to contempo rary culture . This volume gives the student and non - specialist a clear , thoughtful , and highly readable introduction to the basic doctrines of the Christian faith .