I want to know the answer to the following question:
What are the three things John Herschel maintains need to be shown to allow for a mechanism be called a true cause?
All the background I'm provided with is that "The structure of Darwin's argument showed the influence of John Herschel, whose philosophy of science maintained that a mechanism could be called a vera causa (true cause) if three things could be demonstrated: its existence in nature, its ability to produce the effects of interest, and its ability to explain a wide range of observations.". Is that enough to answer the question?
Answer: yes