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108 letters in canada 2002 university of toronto quarterly, volume 73, number 1, winter 2003/4 evidence for his attitude towards the French Revolution in 1790, when health and blindness forced him to stop painting. As Richard Wendorf demonstrated, by then Reynolds clearly was in Burke=s camp regarding the French revolution. It is imprudent to praise someone as in the >progressive= intellectual tradition of John Milton, who defended regicide and served a militarist, intolerant, theocratic government. Patterson=s stark division between Good Whigs who are liberal and democratic and Bad Tories who are conservative and reactionary is simplistic and unhistorical. Let us test Patterson=s hypothesis or, rather, her assumed truth. The eighteenth century included a brilliant man of letters who transcended his humble origins through his own efforts, believed in progress, opposed censorship, published parliamentary debates, toasted the next insurrection of the enslaved negroes, excoriated colonialism and imperialism, encouraged women writers, opened his home, purse, and heart to the poor, and mocked Sir Joshua=s social pretensions and gold-laced sitters, who would not be missed if >extirpated.= That is the man whom Annabel Patterson describes as >the inveterate [>long continuance of any thing bad=] Tory Dr. Johnson.= (HOWARD D. WEINBROT) Richard Johns. A Theory of Physical Probability University of Toronto Press. vi, 260. $85.00 The role of probability and statistics in the study of physical phenomena has a long and well-established history. Probability was used to describe the behaviour of physical systems in a formal sense as early as the eighteenth century with the introduction of statistical mechanics, but probability took centre stage in physics with the discovery of quantum mechanics in the early twentieth century. So it is with much enthusiasm that this reviewer, an experimental particle physicist with an interest in probability and statistics, waded into A Theory of Physical Probability, a monograph by philosopher Richard Johns, which promised to be an >investigation of physical probability, the kind of probability involved in irreducibly random processes.= The book is organized into four main sections: The first section defines formally >logical probability,= a framework that is an extension of the traditional Keynesian concept of the same name. Logical probability is then used to define the >causal theory of chance,= a definition of probability that could be applied to describe physical phenomena. The last two sections of the book explore the application of this theory to classical statistical mechanics and quantum mechanics in this new language. The causal theory of chance is based on a logical framework in which one can identify epistemological relationships between processes or systems and the phenomena they cause. Having this relationship formalized in the humanities 109 university of toronto quarterly, volume 73, number 1, winter 2003/4 language of his logical probability, Johns then develops the concept of the >chance= of a particular event. He defines chance as being a degree of belief of the outcome. Although quite attractive to a subjective Bayesian, I found his operational definition of degrees of belief (as the value of a contract or bet) to be difficult to connect to what we typically would employ as probabilities in a physical context. The latter are often defined classically in terms of the limiting frequencies of the occurrence of an event given an ensemble of similarly prepared systems. He does show how one can make the connection between his definition of chance and frequencies, and he carefully constructs a formal system based on this definition, showing that it satisfies the standard Kolmogorov axioms of probability. The last two topics in the book are perhaps the most interesting to the physicist. Unfortunately, the applications of the causal theory of chance to physical systems are somewhat limited. In the case of classical stochastic mechanics, Johns uses boundary conditions and Lagrangian mechanics to define classical states of motion uniquely, but he creates an unconvincing argument to reconcile the time-invariance of physical laws (i.e., they operate the same regardless of whether we go forward or backward in time) with the >arrow of time= (that many phenomena occur in nature only as time marches forward). He invokes the concept of entropy without ever defining what he means by it in...


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