The two men attended meetings of the Durban Joint Council and held office in the Natal Teacher's Association, of which Matthews eventually was elected president.

After Davidson Don Tengo Jabavu’s retirement in 1944, Matthews was promoted to Professor and became head of Fort Hare’s Department of African Studies.

At the time he also became a member of the Native Representative Council, a purely advisory body that has been condemned as a “toy telephone”.

In June 1952, on the eve of the Defiance Campaign, he left South Africa for a position as visiting professor at New York's Union Theological Seminary.

Although he did not attend the Congress of the People in 1955, he assisted Lionel "Rusty" Bernstein in drawing up the Freedom Charter that was adopted there.

Denis Goldberg credits Matthews with having been one of the driving forces behind the proposal for gathering and documenting the wishes of the people for the Charter.

He resigned his post in protest against the passage of legislation that reduced the university to a status of an ethnic college for the Xhosa community only.

In 1961, Matthews moved to Geneva, Switzerland after being selected as secretary of the Africa division of the World Council of Churches.