The glossary is written precisely, which at the same time means vaguely. It is unavoidable because the technical terms cannot be explained without mathematics. Therefore to be precise, one has to tell less details to avoid being misleading. Once again, Hawking asserts his atheist standpont as well as his disappointment to modern philosophy on the quest of reality. Science does annexed the territories of philosophy in the study of observables, but there the regime of unobservables is still spacious. Though the empiricism of the book is over-simplified, a clear description of scientific method was told. It is important that it is so fundamental to be neglected by most readers, or even scientists.