"In his 1852–3 novel Bleak House, Charles Dickens popularised the term telescopic philanthropy." source: https://en.metapedia.org/wiki/Telescopic_philanthropy

Middlemarch started serial publication in 1871. So George Elliot gets to allude to telescopic philanthropy, confident that her audience will be familiar with "the wag's definition of a philanthropist" and get her dig.