It has lately been objected to me, in studiously courteous terms of course, that I borrow from other books, and am a plagiarist.

To this I reply that I borrow facts from every accessible source, and am not a plagiarist.

The plagiarist is one who borrows from a homogeneous work: for such a man borrows not ideas only, but their treatment.

He who borrows only from heterogeneous works is not a plagiarist.

All fiction, worth a button, is founded on facts; and it does not matter one straw whether the facts are taken from personal experience, hearsay, or printed books; only those books must not be works of fiction.
Ask your common sense why a man writes better fiction at forty than he can at twenty.