QUANTUM METAPHYSICS - E-thesis

depend on that body’s velocity. Newton’s account of mass in his third law is, however,
notoriously unsatisfactory. His definition of mass as the product of a body’s density and volume
is quite useless since the density of a body is commonly defined in terms of its mass and volume.
Newton’s third axiom is not a literal definition of ’mass’, and Ernst Mach was the first to
propose the definition which has been widely adopted. Mach equated the ’relative masses’ of
bodies with the ’negative inverse ratio of their mutually induced accelerations’. As has been
repeatedly emphasised, the constancy of this ratio is not actually a matter of definition, and it is
in the affirmation of this constancy that the main burden of the third axiom lies. 267
3.1.2. Determinism
Closely associated with the study of mechanism, the concept of determinism traditionally refers
to such lawful order on the basis of which later events are predestined or ”determined” by what
has gone before. Classical mechanics is the generally acknowledged paradigm of a deterministic
theory. Viewed in a quite general way, a scientific theory is deterministic if it describes a certain
type of system behaviour against time with the assistance of deterministic laws. 268 In their
Newtonian form, the equations of motion assert that the time rate of change in the momentum of
each mass point belonging to a given physical system is dependent on a definite set of other
factors. In relation to time, the basic laws of classical mechanics are deterministic both forwards
and backwards. Even though the word ”cause” does not appear in these equations, they are
sometimes said to express ”causal relationships” simply because they assert such a functional
dependence of the time rate of- hange in one magnitude (i.e. momentum) upon other
266 Nagel 172, 173. Cartesian physics is the expression of an ideal that can even be termed “extreme”. It restricts
genuine mechanical explanations solely to explanations in terms of action through contact. The various specific
differences between substances must themselves be ultimately explained exlusively in terms of spatiotemporal
differences in the microscopic structures of those substances. Althought it was Newton who propounded the theory
of gravitation, he did not regard it as completely satisfactory because it involved the notion of ”action at a distance”.
Apparently Newton also desired, something that was made quite explicit by Descartes and his followers, a theory of
mechanics which employs only force-functions that correspond to action through contact. Nagel 1961, 171.
267 Trusted 1991, 94-95. Nagel 1961, 167, 170, 192-193.
268 In physics, determinism refers to circumstances in which a certain precondition (as given by certain boundary
conditions) always leads to the same dynamic state.
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