After Returning to England Following the Voyage of the Beagle

After returning to England following the voyage of the Beagle, Darwin continued to struggle with the
Mechanism of evolution. A breakthrough came when he read the work of ________ on the principle of
_______.

A) Kant . . . Heteronomy
B) Kant . . . the synthetic a priori
C) Leibniz . . . petites perceptions
D) Malthus . . . population growth