Mark Jefferson was an extremely private person who rarely expressed opinions about politics, the exception were his views on Germany and World War I. Jefferson expressed his rare political opinions in writing both before and long after he was chosen for the peace delegation.
In a January 1918 letter to his daughter Phoebe, Jefferson stated that a rushed peace that was rushed would have Germany "start preparing again for a successful conquest of the world."
After the peace negotiating process, Jefferson was disturbed by the redistribution of territories, especially the ones taken from Russia. In a 1943 article, Jefferson commented that the territories taken from Russia and Germany by force may have long-lasting repercussions.
Letters to his children during the conference as well as articles written before and after World War I can be found in the Mark S.W. Jefferson papers.