After graduation from Yale in 1884, Veblen was essentially unemployed for seven years. Despite having strong letters of recommendation, he was unable to obtain a university position. It is possible that his dissertation research on "Ethical Grounds of a Doctrine of Retribution" (1884) was considered undesirable. However, this possibility can no longer be researched because Veblen's dissertation has been missing from Yale since 1935. Apparently the only scholar who ever studied the dissertation was Joseph Dorfman, for his 1934 book "Thorstein Veblen and His America". Dorfman says only that the dissertation, advised by evolutionary sociologist William Graham Sumner, studies such evolutionary thought as that of Herbert Spencer, as well as the moral philosophy of Kant. Some historians have also speculated that this failure to obtain employment was partially due to prejudice against Norwegians, while others attribute this to the fact that most universities and administrators considered him insufficiently educated in Christianity. Most academics at the time held divinity degrees, which Veblen did not have. Also, it did not help that Veblen openly identified as an agnostic, which was highly uncommon for the time. As a result, Veblen returned to his family farm, a stay during which he had claimed to be recovering from malaria. He spent those years recovering and reading voraciously. It is suspected that these difficulties in beginning his academic career later inspired portions of his book "The Higher Learning in America" (1918), in which he claimed that true academic values were sacrificed by universities in favor of their own self-interest and profitability.