ose
involved in the existence of plants, animals, and inorganic bodies,
must, as far as possible, be traced to causes; and so, of course, must
the relative positions of objects in space at any time: and what
Co-existences remain do not admit of methodical inductive treatment;
they will be briefly discussed in chap. xix.

Causation, then, is that mode or aspect of the Uniformity of Nature
which especially concerns us in Induction; and we must make it as
definite as possible. It is nothing occult, but merely a convenient name
for phenomena in a particular relation to other phenomena, called their
effect. Similarly, if the word 'force' is sometimes used for convenience
in analysing causation, it means nothing more than something in time and
space, itself moving, or tending to move, or hindering or accelerating
other things. If any one does not find these words convenient for the
purpose, he can use others.

Sec. 2. A Cause, according to Mill, is "the invariable unconditional
antecedent" of a given phenomenon. To enlarge upon this:

(1) A Cause is _relative to a given phenomenon_, called the Effect.
Logic has no method for investigating the cause of the universe as a
whole, but only of a part or epoch of it: we select from the infinite
continuum of Nature any portion that is neither too large nor too small
for a trained mind to comprehend. The magnitude of the phenomenon may be
a matter of convenience. If the cause of disease in general be too wide
a problem, can fevers be dealt with; or, if that be too much, is typhus
within the reach of inquiry? In short, how much can we deal with
accurately?

(2) The given phenomenon is always _an event_; that is to say, not a new
thing (nothing is wholly new), but a change in something, or in the
relative position of things. We may ask the cause of the phases of the
moon, of the freezing of water, of the kindling of a match, of a deposit
of chalk, of the differentiation of species. To inquire the cause of
France being a republic, or Russia an autocracy, implies that these
countries were once otherwise governed, or had no government: to inquire
the cause of the earth being shaped like an orange, implies that the
matter of the earth had once another shape.

(3) The Cause is _antecedent_ to the Effect, which accordingly is often
called its _consequent_. This is often misunderstood and sometimes
disputed. It has been said that the meaning of 'cause' implies an
'effect,' so that until