I thank you for your impression on my views.

Every criticism from a good man is of value to me.

What you hint at generally is very, very true: that my work will be grievously hypothetical, and large parts by no means worthy of being called induction, my commonest error being probably induction from too few facts.

I had not thought of your objection of my using the term "natural selection" as an agent.

I use it much as a geologist does the word denudation--for an agent, expressing the result of several combined actions.