on human nature

The evidence was damning, and yet Lord Emsworth found himself once more prey to doubt. Of the blackness of Sir Gregory Parsole-Parsole's soul he had, of course, been long aware. But could the man actually be capable of the Crime of the Century? A fellow landowner? A Justice of the Peace? A man who grew pumpkins? A Baronet? [summer lightning]

Do you suppose a fellow changes his nature just because a cousin of his dies and he comes into a Baronetcy? [summer lightning]