A selection of the best from recent issues of the Philosopher

The new book opens with a Foreword entitled 'Forward!' in which our author characterizes thought experiments as 'that special kind of theory that predicts particular consequences given certain initial starting points and conditions'. Cohen does not think that it is appropriate to draw a sharp distinction between empirical experiments and thought experiments. He suggests both 'are tests devised either to explore intuitions about how the world works - or to destroy them...' adding: 'The characteristic thing about both real and thought experiments is that you control and limit the circumstances and conditions for the test, so as to pick out just one variable or one unknown. The key difference is that in the latter, everything is set out not in reality but merely in the imagination. The circumstances are described, not created, and the action is imagined, not created.' 

Cohen's broad conception of a thought experiment enables him to select a highly heterogeneous variety of examples of the genre. One gets a taste of the importance of the subject in the Introduction of the book entitled 'Deep Thought - a brief history of thought experiments' which provides historical evidence for what may appear a surprisingly creative use to which this technique of inquiry was put throughout the development of philosophical, scientific and also ethical thought. 

The author proceeds to the main part of the book, which comprises an A - Z series of 26 sections, beginning with 'A is for Alice and Astronomers Arguing about Acceleration', followed by 'B is for Bernard's [. Bernard Williams'] Body-Exchange Machine' and so on, all the way to 'Z is for Zeno and the Mysteries of Infinity'. Each section offers a brief exposition of a particular thought experiment and then a philosophical discussion of the topic liberally punctuated with irreverent jeux d'esprit. There follows a chapter on 'Notes for Experimenters' which includes a highly suggestive section on 'How to Experiment' - in my judgment the most original part of the book.

The interest of the book is clearly dependent on, and derived from, the interest and value of the technique of thought experiment in science and philosophy. On this last point Cohen is emphatic. 'It is no exaggeration to say,' he exaggerates, 'that the whole of modern science is built upon the surprisingly modest foundation of half a dozen of the thought experiments included here' - or so it strikes me. I would say rather that scientific work involves a dynamic interplay between, on the one hand, empirical data in various degrees of rawness accumulated by scientists in response to a problem and provisionally conceived, described, classified, analysed and so on, in a language impregnated by low-level theory (For instance, Darwin's observation and study of fossils and bones of long-extinct animal species or Brownian motion described in terms of the kinetic theory of fluids), and on the other, intellectual efforts to bring these phenomena under explanatory schemata of increasing scope and predictive power which can be tested against experience (for example, the theory of evolution or atomic theory of matter and the relevant mathematical models). 

This book is not addressed to professional philosophers, but is by no means a beginners' piece, much less reading matter for Aunt Edna to take on the train. It will best be appreciated by readers who already have some understanding of philosophy and scientific methodology, and have developed some taste for conceptual inquiry. For all the clarity of the writing, the text is never facile - indeed, it is occasionally hard-going and controversial in its interpretation of particular thought experiments. Like previous cohens, Wittgenstein's Beetle brings together diverse material which displays a unity of viewpoint and a seriousness of treatment, embellished with wit and delightful comic invention. 
 

Reviewed by Zenon Stavrinides