There are three main streams of metaphysics in the west: the ancient,
the classical religious, and Darwinian branch of evolution and natural
selection. There are undoubtedly others, but at least these three try
to analyze the nature of man in scientific or quasi scientific terms.
The ancient branch of metaphysics was laid down by Aristotle who
defined metaphysics as the study of being qua being and a prime mover
unmoved as the first cause of everything. Classical religious dogma
kept the metaphysics and merely replaced the prime mover unmoved by
god, viewing metaphysics and science as extensions of the intentions
of god according to holy writ.
And in perhaps the penultimate chapter in the epistemological
revolution characterizing the post renaissance natural science,
Charles Darwin redefined man not according to ancient or classical
religious assumptions regarding animal, man, and god but according
to biological linkage between man and animals instead, thus relegating
metaphysics to the study of evolution of species and the idea of
evolution as a first cause.
What's noteworthy in all three instances, however, is that no one ever
proved anything regarding first causes. Aristotle's first cause, the
prime mover unmoved was simply an imaginary construct, as was god.
The ideas of a prime mover unmoved and god were merely forensic
devices without mechanical support.
Evolution, on the other hand, certainly had evidentiary mechanical
support in the origin of species, but nothing in the origin of species
says definitely what a first cause is of necessity. Evolution and
natural selection themselves are ideas predating Darwin's connection
of them to the origin of species. Biological speciation might be a
vehicle of natural selection. But that doesn't mean it is the only
possible vehicle of natural selection, evolution, or the necessary
first cause of everything.
In other words, the biological origin of species could be true without
proving the direct connection of man to animal in mechanical terms.
Evolution could just as easily provide the transition from animal to
man just as between plant and animal. And we would still be left with
the distinct and separate categories however they originated. Darwin
proved there was no supernatural or divine intervention needed in the
mechanical transition. But he did not prove there was no transition.
The only cause which supplies its own proof as first cause is the idea
of differences and cognates of differences: negation, contradiction,
not, etc. and that principle compounded in terms of itself. Neither
Aristotle's prime mover unmoved nor god is proven of itself. Nor are
evolution and the natural selection of species proven with respect to
the categories and transitions between the categories.
The only thing proven of itself as the source and first cause of
everything are differences and cognates of differences. And it is
in terms of these elements that the categories of being are to be
examined and explained in strict mechanical terms of one another.
Regards - Lester