ed successively in the history of Philosophy, and which have
had for their avowed object the explanation of the _connection between
God and Nature_, or the conciliation of Theology with Science.[192]
Hence, first of all, the theory of "occasional causes," as taught by
Father Malebranche, with the laudable, but, as we think, mistaken,
design of vindicating the Divine agency in Providence by virtually
superseding every other power in Nature;--a theory which represents
physical agencies as the mere _occasions_, and God as the sole _cause_
of all changes, which teaches that a healthy eye, with the presence of
light, is not the cause of vision, but the occasion only of that Divine
interposition by which alone we are enabled to see, and that a man's
desire or volition to walk is not the cause of his walking, but the
occasion merely of that Divine interposition which alone puts the proper
muscles in motion. Hence, secondly, the theory of "preestablished
harmony" as taught by Leibnitz;--a theory which was mainly designed to
explain the relation subsisting between the soul and the body, but which
involves principles bearing on the general doctrine of cause and effect,
and applicable to the relation subsisting between God and His works.
This theory teaches that mind and body, although closely united, have no
real influence on each other, that each of them acts by its own
properties and powers, and that their respective operations exactly
correspond to each other by virtue of a "preestablished harmony" between
the two, just as one clock may be so adjusted as to keep time with
another, although each has its own moving power, and neither receives
any part of its motions from the other. This theory, therefore, denies
everything like causal action between mind and matter; and when it is
extended, as it may legitimately be, to the relation between God and the
world, it would seem to imply the coequal existence and independence of
both, and the impossibility of any causal relation between the two. The
manifest defects of these theories have given rise to a _third_, which,
in one of its forms, has been generally adopted by Divines,--the theory
of "instrumental causes."

This theory has assumed two distinct and very different forms. In the
first, all natural effects are ascribed to powers _imparted_ to created
beings, and _inherent_ in them; that is, to powers which are supposed to
have been conferred at the era of Creation, and to be stil