A key figure in making the pilgrimage possible was Jérôme Lejeune, the geneticist renowned for discovering that Down syndrome is caused by trisomy of the 21st chromosome. He calmed the organizers' fears "about possible harmful effects of the pilgrimage on the psychology of young people with disabilities" and lent his considerable reputation to amplify the initiative's reach. As Marie-Hélène Mathieu recounts in Mai più soli (Jaca Book 2012), bringing together so many fragile people in one place raised serious concerns about managing their health. Equally important was the contribution of Dr. Préaut, a psychiatrist with the Ark who had witnessed the benefits of Special Olympics for participants with intellectual disabilities and their companions. The pilgrimage could offer a chance to overcome prejudice and finally experience true community.
Working with Marie-Odile Réthoré, a physician specializing in the development of children with trisomy, Lejeune (declared a Servant of God by the Catholic Church in January 2021) insisted on including in the pilgrimage program a conference for doctors and educators on The Psychological Impact of Rejection and Acceptance for People with Intellectual Disabilities. At a press conference on June 4, 1970, curious journalists asked him to elaborate on the initiative. Describing it as "a school of hope" whose "fruits" he would be delighted to witness, the geneticist explained "how deeply segregation can fracture a personality, and conversely, how love can rebuild it". Indeed, as Mathieu notes, during the conference he chaired, the diverse assembly of educators and physicians expressed a striking impression of the pilgrimage's atmosphere: it was living proof of how the quality of welcome transformed the lives of people with disabilities. And those who stood beside them.