QUANTUM METAPHYSICS - E-thesis

future development. 272
It is, however, evident that Laplace was here simply expounding the feature of mechanics that
makes it a deterministic theory. He was guilty of a serious non sequitur when he declared that
”nothing would be uncertain” even if he did not know whether the divine intelligence was able to
analyse all the traits of physical objects in terms of the variables that constitute the mechanical
state of the system. Moreover, when physicists of the 1800s subscribed to determinism as an
article of scientific faith, most of them took as their ideal of a deterministic theory one which
defines the state of a physical system in the manner employed by particle mechanics. In
considerable measure, this ideal continues to control current discussions of causality and
determinism in physics. Even if the identification of determinism with mechanism is a mistaken
one, it is frequently assumed that the mark of a deterministic theory is its use of mechanical
definitions of state. If the determinism were to be severely limited just to determinism with
respect to mechanical states, all the possible traits of physical objects – such as their optical,
thermal and electromagnetic properties – would be definable in terms of the variables that
constitute the mechanical state of the system. 273
Mechanics does not rest on the assumption that such an analysis is in fact possible in terms of
particle mechanics. Nor does the determinism of mechanics exclude the possibility that
alterations in the mechanical state of the system may be consequences of changes in the
properties of a system that cannot be analysed in this way. It is evident that classical mechanics
is not the only deterministic theory in modern physics. For example, electromagnetic field
theory, statistical mechanics and general relativity theory, and more recently quantum theory,
involve modes of state description that diverge from the canonical one. A theory is properly
labelled as deterministic if analysis of its internal structure shows that the theoretical state of a
system at a single instant logically determines a unique state of that system at any other instant.
Given the values of the state variables for some initial period, the theory should logically
determine a unique set of values for those variables for any other period. If a causal theory is
characterised as being in some sense ”indeterministic”, the alleged indeterminism must be
explicated in terms of some special features distinguishing the state-description which the theory
272 In practical terms, the calculations soon become very complicated. Chaos theory also implied difficulties with
the predictability of a deterministic system, since a minute change in the initial figures may result in huge variations
in the results.
102