Ninian Smart was a founding figure in British secular religious studies. This review of 'world philosophy' came at the very end of his life as perhaps a summation of at least one part of his life's work - a particular approach to religion as containing within it varieties of philosophy.
The reader should be warned, therefore, that this is a book largely of the many different potentialities of philosophy as justifications for belief and culture rather than any set of positions about philosophy as a professional investigation of the truth or challenge in the cause of truth.
Smart is instinctively non-judgmental and tolerant, the epitome of the kindly Scottish relativist who refuses to get off the fence even when it is a matter of saying whether God exists or not. The question is irrelevant to him - the issue is whether those he studies believe what they believe.
Once this position is established, then the book can abandon the study of religion qua religion and look at the many varieties of judgement and criticism that we call philosophy and that make up the human religious condition along equally non-judgemental globalist lines.
From this perspective, the book is useful as a reference work but Smart has taken on too big a task, especially as he insists on giving broadly equal value to all parts of the world and all traditions. The result is (as with so many general companions to philosophy) short-handing and so obscurities.
Still, as sets of summary of the many components of human belief and the 'thinking' that goes into sustaining them, the book is better in the library than out of it. The extensive bibliography alone provides a baseline, at the end of the last century, for further study.