What are primary and secondary causalities?

An expert in Medieval Philosophy, Armand Maurer, traces their history, backwards from Charles Darwin.  He publishes an article in The Review of Metaphysics (volume 57(3), 2004, pages 506-511).

Darwin thinks that his theory of evolution endowed living beings with secondary causalities more profound and subtle than hitherto contemplated.  Creatures have the ability to produce new substances on their own accord.  That new substance is a new species or genus.

Before this, philosophers never confront the question of evolution.  So, secondary causality belongs to creatures, in accordance to the Will and Presence of God, the primary cause.  Secondary causes are living creatures getting on with their lives.

As it turns out, that is also what living creatures do according to Darwin’s theory of evolution.  The difference is that their survival is subject to natural selection, especially in regards to exploiting their niche.

Surely, there must be consistency here, besides that both medieval philosophers and the educated folk of Darwin’s time use the terms, primary and secondary causes.

Maurer ends with Maritain, who publishes and exploration of the role of primary and secondary causes in Darwin’s schema.

The introduction and five parts follow the Maurer’s arguments, not point by point, but according to the timeframe that he articulates.  The story begins with the Book of Causes, a Neoplatonic work written around Baghdad a few decades after the death of the Abbasid caliph, Al-Mamun.