The ethos of the aristocracy as exemplified in the English public school greatly influenced Pierre de Coubertin.[130] The public schools subscribed to the belief that sport formed an important part of education, an attitude summed up in the saying mens sana in corpore sano, a sound mind in a sound body. In this ethos, a gentleman was one who became an all-rounder, not the best at one specific thing. There was also a prevailing concept of fairness, in which practicing or training was considered tantamount to cheating.[130] Those who practiced a sport professionally were considered to have an unfair advantage over those who practiced it merely as a hobby.[130]
The exclusion of professionals caused several controversies throughout the history of the modern Olympics. The 1912 Olympic pentathlon and decathlon champion Jim Thorpe was stripped of his medals when it was discovered that he had played semi-professional baseball before the Olympics. His medals were posthumously restored by the IOC in 1983 on compassionate grounds.[131] Swiss and Austrian skiers boycotted the 1936 Winter Olympics in support of their skiing teachers, who were not allowed to compete because they earned money with their sport and were thus considered professionals.[132]
As class structure evolved through the 20th century, the definition of the amateur athlete as an aristocratic gentleman became outdated.[130] The advent of the state-sponsored "full-time amateur athlete" of the Eastern Bloc countries further eroded the ideology of the pure amateur, as it put the self-financed amateurs of the Western countries at a disadvantage. Nevertheless, the IOC held to the traditional rules regarding amateurism.[133] Beginning in the 1970s, amateurism requirements were gradually phased out of the Olympic Charter. After the 1988 Games, the IOC decided to make all professional athletes eligible for the Olympics, subject to the approval of the IFs.[134] As of 2012, the only sports in which no professionals compete is boxing and wrestling, although even this requires a definition of amateurism based on fight rules rather than on payment, as some boxers and wrestlers receive cash prizes from their National Olympic Committees.