In this short and rather dense book, John Barrow attempt to provide the beginnings of an answer to the question of a unified theory of everything. Breaking such a topic down into sections is both necessary and complicated, but Barrow divides the lectures into eight parts: laws of Nature, initial conditions, forces and particles, constants, broken symmetries, organizing principles, selection biases and categories of thought. Each lecture serves as both an introduction to the topic and a thorough examination of it, as Barrow seeks to evaluate the current state of the field whilst giving a broad overview of how the drive towards a single unified theory finds expression in each of the topics under discussion. For example, in the chapter on the laws of nature, Barrow offers a rather brisk summary of some of the arguments from Boscovich, Newton and others before finishing with an examination of string theory. The problem with seeking a single unified theory from the laws of Nature is it reveals a prejudice for timeless universals over temporal particularity and given the temporal nature of the universe this seems like something of an oversight. One seemingly vital question concerns mathematics and whether or not maths is adequate for describing the deepest levels of reality, especially given Gödel’s incompleteness theorem – Gödel’s point, whilst holding true for pure mathematics, is perhaps not as applicable to the messier, material maths which connect to experimental and particle physics.  From there Barrow goes on to consider whether time and space predate the universe – a question highlights the philosophical implications of the search for a theory of everything. 

It is in the philosophical implications of the argument unfolded that perhaps these lectures are not as forceful as they could be, as Barrow generally shies away from making statements too far removed from mathematical or physics. Those seeking definitive answers are liable to be left somewhat disappointed as Barrow acknowledges that, at present, all that physics can offer are approaches to problems which are promising or less so.  A pressing problem is the limitations of what can be observed – there is a great deal more that is posited to exist and so it is something of a mistake to assume that the observed universe is the typical state of things. At the close of the book, Barrow acknowledges that ‘there is no formula that can deliver all truth' (246) and it is this which allows space for the continued philosophical investigation of the implications of Barrow’s fascinating insights offered in this lecture series.