What do we know?

Ptolemy's epicycles, conceived to reconcile the planets' apparent motion with the belief that they revolved round the Earth, worked nicely for navigators but suffered from one drawback – the theory was efficacious, but incorrect, concealing the truth of the planets' actual motion. 'The Ptolemy Problem' is one of a dozen such difficulties which Grayling illustrates throughout this authoritative work to help us identify problems with what we think we know.

What do we know? How have we come to know it? We are taken through a detailed history of how we have arrived at the current state of play and pitfalls on the way. There follows an inspection of the landscape of ignorance which our increased knowledge paradoxically reveals.

Grayling's grasp of modern physics and cosmology is detailed and impeccable, to the extent that non-scientists may struggle with the odd paragraph. Grayling first takes us from the earliest attempts to construct stone tools to our current efforts to reconcile quantum mechanics with general relativity. Next, Grayling marvels at the vast expansion of our understanding of what the past is – until very recently, history was what the Bible said it was, fitting into just 6000 years. He carefully distinguishes between history as the study of the past and history as the past itself, the two often having been confused; he acknowledges the great but inevitable difficulty besetting any study of history – that we see and judge the past through our current prejudices. As these alter over time, our construction of history changes; he delineates where this is necessary, such as the revision of our understanding of colonialism, and where it is egregious, such as Holocaust denial.

Grayling then brings a philosopher's clarity to the conceptual morass surrounding concepts such as 'consciousness', 'mind' and 'self'. Whilst the behaviourists are described, there is no reference to the analytical schools and neither Freud nor Jung get a mention. This seemed an odd omission, so I asked Grayling about it. He explained that 'the empirical basis in both cases is slender and anecdotal, and the connection to empirical brain science tenuous'. He also thought that they held 'the same kind of relationship to contemporary neuroscience as hypothesising about the structure of the universe in pre-Copernican cosmology bore to cosmology from the 17th century onwards'.

Some clinicians and even neuroscientists may well disagree. The numinous landscape of the human psyche as revealed by depth psychology, stretching out in all its exuberant irrationality, is another ungraspable frontier of knowledge, the existence of which the more extreme rationalists prefer not to acknowledge. Whilst some of the concepts of depth psychology may be Ptolemaic in nature, they are much better than nothing for those who navigate these areas.

Any gripes aside, this is a masterful, scholarly yet accessible work which I greatly enjoyed reading, and I imagine that many of my colleagues will too.

- Reviewed by Galen Ives, Consultant Clinical Psychologist