rms
are so varied, and the uses to which they are applied so unlike each
other."[270] All these are homologous in structure--they are formed
after an ideal archetype or model, but that model or type is variously
modified to adapt the animal to the sphere of life in which it is
destined to move, and the organ itself to the functions it has to
perform, whether swimming, flying, walking, or burrowing, or that varied
manipulation of which the human hand is capable. These varied
modifications of the vertebrated type, for special purposes, are
unmistakable examples of final causation. Whilst the silent members, the
rudimental limbs instanced by Oken, Martins, and others--as fulfilling
no purpose, and serving no end, exist in conformity to an ideal
archetype on which the bony skeletons of all vertebrated animals are
formed,[271] and which has never been departed from since time began.
This type, or model, or plan, is, however, itself an evidence of
_design_ as much as the plan of a house. For to what standard are we
referring when we say that two limbs are morphologically the same? Is it
not an _ideal_ plan, a _mental_ pattern, a metaphysical conception? Now
an _ideal_ implies a mind which preconceived the idea, and in which
alone it really exists. It is only as "an _order of Divine thought_"
that the doctrine of animal homologies is at all intelligible; and
Homology is, therefore, the science which traces the outward embodiment
of a Divine Idea.[272] The principle of intentionality or final
causation, then, is not in any sense invalidated by the discovery of "a
unity of plan" sweeping through the entire universe.

[Footnote 270: Carpenter's "Comparative Physiology," p. 37.]

[Footnote 271: Agassiz, "Essay on Classification," p. 10.]

[Footnote 272: Whewell's "History of Inductive Sciences," vol. i. p.
644; "The Reign of Law," p. 208; Agassiz, "Essay on Classification," pp.
9-11.]

We conclude that we are justly entitled to regard "the principle of
intentionality" as a primary and necessary law of thought, under which
we can not avoid conceiving and describing the facts of the
universe--_the special adaptation of means to ends necessarily implies
mind_. Whenever and wherever we observe the adaptation of an organism to
the fulfillment of a special end, we can not avoid conceiving of that
_end_ as foreseen and premeditated, the _means_ as selected and adjusted
with a view to that end, and creative energy put forth to secure