only possible alternative. If there be supposed to be no
connection between two phenomena constituting one of those invariable
sequences which we are accustomed to denominate cause and effect, the
sequence which they constitute must needs be an unconnected sequence,
and the only reason for styling one of the phenomena a cause is, that it
is an antecedent which the other invariably follows. But according to
this, as has been pointed out over and over again, day would be the
cause of night, and night the cause of day, and tidal flux and reflux
likewise would be each other's causes; and Mr. J. S. Mill has therefore
proposed to interpolate a word, and to define the cause of a phenomenon
as 'the antecedent on which it (the phenomenon) is invariably and
_unconditionally_ consequent.'[30] I must, however, confess myself
unable to perceive how the definition is improved by this emendation.
There is not, and cannot possibly be, such a thing as _unconditionally_
invariable sequence, as, indeed, Mr. Mill himself virtually admits by
expressly assuming as an indispensable condition of all causation that
'the present constitution of things endure.' But if, notwithstanding the
presence of this indispensable condition, it be permissible to call any
sequence unconditionally invariable, then the sequences of night upon
day and of day upon night are such sequences, and day and night continue
consequently entitled to be styled each other's causes as much under the
amended as under the original definition. For as long as 'the present
constitution of things endures,' that is, as long as the earth continues
to revolve on its axis, and the sun continues to shine, and no opaque
substance intervenes between earth and sun, day and night will continue
to be as invariably and unconditionally each other's antecedents as
sunlight will continue to be the antecedent or concomitant of day.
True, Mr. Mill denies that the earth's diurnal motion is part of the
present constitution of things, because, according to him, 'nothing can
be so called which might possibly be terminated or altered by natural
causes:' but, if so, then neither ought sunlight to be so called, for it
too quite possibly may, nay, in the opinion of many philosophers, most
certainly will, be extinguished eventually by natural causes. If day
ought not to be called the unconditionally invariable consequent of
night merely because it would cease to be so if the earth were to cease
turning on i