One of the interesting features of the 20th century is the union of metaphysical naturalism and what we tend to term 'post-modernism.'
Advocates of the latter tend to nuance it, so any attempted characterization will doubtlessly meet with resistance.
But one of its central features is the replacement of substance ontology--the idea that there are things in the world that we can know as things--with narratival, relational, personal or social constructions.
We're allergic to talking about the body and soul and soul as existing substances, but just fine describing power structures and social forces. That's the post-structuralist option. Or we don't want to talk about human essences, but rather focus on our freedom to determine our own identities by virtue of our choice. Hello, existentialism.
Both threads share an antipathy toward the metaphysics of essences--that things have essences that are independent of their social construction or their self-determination. And to the extent that this antipathy characterizes post-modernity, metaphysical naturalism (best supported by the Darwinian story) has proved a strong ally.
This reduction of the formal essence of life to the vanishing-point of a mere vital momentum without specific original content, and correspondingly the throwing open of the indefinite horizon of situation for the evoking of possibilities which were not pre-existing potentialities, have a familiar ring to those with contemporary philosophies of man. Indeed nineteenth-century evolutionism, which completed the Copernican revolution in ontology, is an apocryphal ancestor (along with the more official ones) of present-day existentialism. The latter's encounter with "nothingness" springs from the denial of "essence" which blocked the recourse to an ideal "nature"of man, once offered in his classical definition by reason homo animal rationale), or in the Biblical one by creation in the image of God. The "image," in the absence of creation, had vanished with the original; and reason had been reduced to a means among means, to be judged by the efficiency of its instrumental role in the survival issue; as a merely formal skill--the extension of animal cunning--it does not set but serve aims, is not itself standard but measured by standards outside its jurisdiction. If there is a "life of reason" for man as distinct from the mere use of reason, it can be chosen only nonrationally, as all ends must be chosen nonrationally (if they cane chosen at all). Thus reason has no jurisdiction even over the choice of itself as more than a means. But use of reason, as a means is compatible with any end, no matter how irrational. This is the nihilistic implication in man's losing a "being" transcending the flux of becoming. Nietzsche's nihilism and his attempt to overcome it demonstrably connected with the impact of Darwinism. The will to power seemed the only alternative left if the original essence of man had evaporated in the transitoriness and whimsicality of the evolutionary process. This is to say, not that Darwinism is the progenitor of existentialism, but that it conforms and contributes to all the other mental factors out of whose total setting existentialism logically grew. We mentioned the major role which evolutionism with the liquidation of immutable species played in the anti-Platonic trend of modern science: existentialism is the most radical conclusion drawn so far from the unreservedly accepted victory of nominalism over realism.
Post-structuralism wasn't around when Jonas was writing, but insofar as remains within the post-Nietschean world, it certainly fits Jonas' description.
There's a lot to unpack in that excerpt, but here's one potential line of further reflection: if it's true that evangelicals don't have a robust doctrine of creation and tend to be nominalists, that would explain the tacit acceptance of metaphysical naturalism on the one hand (combined with an overly robust supernaturalism to explain ethics), and post-modernism on the other.
At least, that's the standard line on evangelicals. Whether it holds is (to me) an open question. But the relationship is at least worth exploring.
(P.S. I am way behind on responding to comments, for which I apologize. I'm travelling this week, which has disrupted my schedule quite a bit. I hope to respond at some point in the next few days.)
Matthew Lee Anderson is an Associate Professor of Ethics and Theology in Baylor University's Honors College. He has a D.Phil. in Christian Ethics from Oxford University, and is a Perpetual Member of Biola University's Torrey Honors College. In 2005, he founded Mere Orthodoxy.