He enjoys the unique distinction of having served in the cabinets of seven Canadian Prime Ministers: Macdonald, Abbott, Thompson, Bowell, Tupper, Borden and Meighen.

[1] Two factors thwarted whatever ambitions he may have had to become Prime Minister himself: his legally questionable marriage in Chicago to his newly divorced former landlady,[2] and his later involvement in a trust company scandal.

He taught in various high schools and seminaries until 1870 when he was appointed Professor of Classics and Ancient Literature in the University of New Brunswick.

Foster retained this position after Macdonald's death and through the successive governments of Prime Ministers Abbott, Thompson, Bowell and Tupper.

He led a group of seven cabinet ministers who resigned temporarily in January 1896 to force the retirement of Bowell, who denounced them as a 'nest of traitors'.

The ultimate origin of "splendid isolation" is suggested in Robert Hamilton's Canadian Quotations and Phrases,[7] which places the Foster quotation beneath a passage from the following paragraph from Cooney's Compendious History of Northern New Brunswick and Gaspé (reprinted in 1896) describing England's situation in 1809–1810 during the Napoleonic Wars:In the midst of this terrific commotion, England stood erect: wrapt up in her own impregnability, the storm could not affect her: and therefore, while others trembled in its blast, she smiled at its fury.

[8]This, in turn, echoes the stoicism of Marcus Aurelius: "Be like the promontory against which the waves continually break, but it stands firm and tames the fury of the water around it.

[10] Following his death, Foster's widow granted Canadian historian William Stewart Wallace permission to produce an authorized biography of her late husband.