What is the trinity and does it really matter? Donald Macleod tells us that it does matter as "it is the model for the way we should live, particularly in our relations with one another." The Bible teaches clearly about the relationship between Father, Son and Holy Spirit. Fully grasping the trinity will always be beyond us, after all it is a divine mystery, but we can understand it better and it is critically important that we do, for if our understanding of God is wrong, it follows that our other ideas may be wrong too. 'The doctrine of the Trinity is not simply something to be believed, but something that ought to affect our lives profoundly', says Donald Macleod in this useful book that teaches us about the concept and implications of the doctrine of the Trinity.