When her mother died on their travels in Syria in 1855, she returned to England to stay with her grandfather, John Manners, the 5th Duke of Rutland, at Belvoir Castle.

Once her children were grown and had moved out of the house, Welby, who had had little formal education, began a fairly intense process of self-education.

It was not unusual for Victorian Englishmen of means to become thinkers and writers (e.g. Darwin, Lord Acton, J. S. Mill, Charles Babbage).

By the late 19th century, she was publishing articles in the leading English language academic journals of the day, such as Mind and The Monist.

was sympathetically reviewed for The Nation by the founder of American pragmatism, Charles Sanders Peirce, which led to an eight-year correspondence between them, one that has been published three times, most recently as Hardwick (2001).

She also corresponded with William James, F. C. S. Schiller, Mary Everest Boole, the Italian pragmatists Giovanni Vailati and Mario Calderoni,[4] F.H.

V; 1898)Welby's concern with the problem of meaning included (perhaps especially) the everyday use of language, and she coined the word significs for her approach (replacing her first choice of "sensifics").

In turn, these corresponded to three levels of consciousness, which she called "planetary", "solar", and "cosmic", and explained in terms of a sort of Darwinian theory of evolution.

Welby had a direct effect on the Significs group, most of whose members were Dutch, including Gerrit Mannoury and Frederik van Eeden.