into a mature and
perfect oak greatly depends on the exterior conditions of soil, and
moisture, light, and heat. By these it may be rendered luxuriant in its
growth, or it may be stunted in its growth. It may barely exist under
one class of conditions, or it may perish under another. The Brassica
oleracea, in its native habitat on the shore of the sea, is a bitter
plant with wavy sea-green leaves; in the cultivated garden it is the
cauliflower. The single rose, under altered conditions, becomes a double
rose; and creepers rear their stalks and stand erect. Plants, which in a
cold climate are annuals, become perennial when transported to the
torrid zone.[6] And so human nature, fundamentally the same under all
circumstances, may be greatly modified, both physically and mentally, by
geographical, social, and political conditions. The corporeal nature of
man--his complexion, his physiognomy, his stature; the intellectual
nature of man--his religious, ethical, and esthetical ideas are all
modified by his surroundings. These modifications, of which all men
dwelling in the same geographical regions, and under the same social and
political institutions, partake, constitute the _individuality_ of
nations. Thus, whilst there is a fundamental basis of unity in the
corporeal and spiritual nature of man, the causes of diversity are to be
sought in the circumstances in which tribes and nations are placed in
the overruling providence of God.

[Footnote 6: See Carpenter's "Compar. Physiology," p. 625; Lyell's
"Principles of Geology," pp. 588, 589.]

The power which man exerts over material conditions, by virtue of his
intelligence and freedom, is also an important element which, in these
studies, we should not depreciate or ignore. We must accept, with all
its consequences, the dictum of universal consciousness that man is
_free_. He is not absolutely subject to, and moulded by nature. He has
the power to control the circumstances by which he is surrounded--to
originate new social and physical conditions--to determine his own
individual and responsible character--and he can wield a mighty
influence over the character of his fellow-men. Individual men, as
Lycurgus, Solon, Pericles, Alexander, Caesar, and Napoleon have left the
impress of their own mind and character upon the political institutions
of nations, and, in indirect manner, upon the character of succeeding
generations of men. Homer, Plato, Cicero, Bacon, Kant, Locke, Newton