usions being the same, namely,
uncontradicted experience. Now when we say, 'If Nature is uniform,
science is true,' the hypothetical character of science appears in the
form of the statement. Nevertheless, it seems undesirable to call our
confidence in Nature's uniformity an 'hypothesis': it is incongruous to
use the same term for our tentative conjectures and for our most
indispensable beliefs. 'The Universal Postulate' is a better term for
the principle which, in some form or other, every generalisation takes
for granted.

We are now sometimes told that, instead of the determinism and
continuity of phenomena hitherto assumed by science, we should recognise
indeterminism and discontinuity. But it will be time enough to fall in
with this doctrine when its advocates produce a new Logic of Induction,
and explain the use of the method of Difference and of control
experiments according to the new postulates.

CHAPTER XIX

LAWS CLASSIFIED; EXPLANATION; CO-EXISTENCE; ANALOGY

Sec. 1. Laws are classified, according to their degrees of generality, as
higher and lower, though the grades may not be decisively
distinguishable.

First, there are Axioms or Principles, that is real, universal,
self-evident propositions. They are--(1) real propositions; not, like
'The whole is greater than any of its parts,' merely definitions, or
implied in definitions. (2) They are regarded as universally true of
phenomena, as far as the form of their expression extends; that is, for
example, Axioms concerning quantity are true of everything that is
considered in its quantitative aspect, though not (of course) in its
qualitative aspect. (3) They are self-evident; that is, each rests upon
its own evidence (whatever that may be); they cannot be derived from one
another, nor from any more general law. Some, indeed, are more general
than others: the Logical Principle of Contradiction, 'if A is B, it is
not not-B', is true of qualities as well as of quantities; whereas the
Axioms of Mathematics apply only to quantities. The Mathematical Axioms,
again, apply to time, space, mental phenomena, and matter and energy;
whereas the Law of Causation is only true of concrete events in the
redistribution of matter and energy: such, at least, is the strict limit
of Causation, if we identify it with the Conservation of Energy;
although our imperfect knowledge of life and mind often drives us to
speak of feelings, ideas, volitions, as causes. Still, the