A Theory of Physical Probability

Dr. Patrick W. Colgan is the director of Research and Natural Lands at
the Royal Botanical Gardens.

Johns, who teaches philosophy at the University of British Columbia, has
prepared an advanced text on how we can approach the issue of
probability. Taking causation as primitive, chance is therefore
derivative, and Johns sets out to derive chance rigorously. He begins by
distinguishing causation and determination, and two faces of chance,
epistemic and physical. Drawing on John Maynard Keynes, Johns tackles
the issues of logic and probability. Potential objections are refuted,
and the work of many probabilists, especially Peter Gдrdenfors, is
drawn on. The formal structure of probability is detailed in axioms and
theorems. Hearkening back to Aristotle’s efficient causation, the
differences between causation and determination are explored, and a
conclusion is that “a cause need not determine its effects.” The
link between language and objects is investigated, in part leading to
the conclusion that existence is not a property.

Next discussed is physical chance, which is linked to relative
frequency both epistemologically and by way of explanation, leading to
an analysis of the theories of Richard von Mises, Karl Popper, and
others. Johns turns next to classical stochastic mechanics, founded on
five postulates of real systems, and assorted special cases.
Correlations are considered both for classical and quantum systems, with
the contributions of various physicists examined state vectors
subsequently analyzed.

Johns, who sees philosophers and physicists working closely together,
has a sharp awareness of how reality lies (e.g., “I view causal
relations as essentially timeless”). With his attention to causation,
chance, determination, and probability, Johns is clearly tackling some
very basic matters, and small wonder that he refers to many thinkers
back to Aristotle. He does so presuming high-level knowledge of
mathematical logic and quantum mechanics on the part of the reader. This
is illustrated when on “EPR” (standing in physics for
Einstein-Podolsky-Rosen correlations) is cited on page 8 without
expansion. Only for advanced readers.