d energy to be
indestructible, we can plainly see that in any particular cases of its
manifestation in sequence-phenomena, the unconditional resemblance between
effects due to similar causes which is formulated by the law of causation
is merely the direct expression of the fact which we had previously
concluded. It seems to me, therefore, that the old-standing question
concerning the nature of causation ought now properly to be considered as
obsolete. Doubtless there will long remain a sort of hereditary tendency in
metaphysical minds to look upon cause-connection as "a mysterious tie"
between antecedent and consequent; but henceforth there is no need for
scientific minds to regard this "tie" as "mysterious" in any other sense
than the existence of energy is "mysterious." To state the law of causation
is merely to state the fact that energy is indestructible.

And from this there also arises at once the explanation and the
justification of our belief in the uniformity of nature. If energy is, in
its relation to us, ubiquitous and persistent, it clearly follows that in
all its manifestations which collectively we call nature, similar preceding
manifestations must always determine similar succeeding manifestations; for
otherwise the energy concerned would require on one or on both of the
occasions, either to have become augmented by creation, or dissipated by
annihilation. Thus our belief in the uniformity of nature, as in the
validity of the law of causation, is merely an expression of our belief in
the ubiquitous and indestructible character of energy.

Such being the case, we may fairly conclude that all these old-standing
"mysteries" are now merged in the one mystery of existence. And deeper than
this it is manifestly impossible that they can be merged; for it is
manifestly impossible that Existence in the abstract can ever admit of what
we call explanation. Hence we can clearly see that, in a scientific sense,
there must always remain a final mystery of things. But although we can
thus see that, from the very meaning of what we call explanation, it
follows that at the base of all our explanations there must lie a great
Inexplicable, I think that the mystery of Existence in the abstract may be
rendered less appalling if we reflect that, as opposed to Existence, there
is only one logical alternative--Non-existence. Supposing, then, our
physical explanations to have reached their highest limits by resolving all
modes of