Hans Jürgen Eysenck (March 4, 1916 – September 4, 1997) was a German-British psychologist who spent most of his career in Britain, best remembered for his work on intelligence and personality, though he worked in a wide range of areas. At the time of his death, Eysenck was the living psychologist most frequently cited in science journals.

Hans Eysenck was born in Berlin, Germany, his mother a film star (Helga Molander) and his father a nightclub entertainer, once voted 'handsomest man on the Baltic coast'. (p8-11). Eysenck was brought up by his grandmother, who was a fervent Catholic, though of Jewish ancestry - a fact he did not know until after her death in a concentration camp (p. 80) An initial move to England in the 1930s became permanent due to his opposition to the Nazi party. "My hatred of Hitler and the Nazis, and all they stood for, was so overwhelming that no argument could counter it."(p 40) Because of his German citizenship, he was initially unable to gain employment, and was almost interned during the war. He received his PhD in 1940 from University College, London (UCL) working in the Department of Psychology under the supervision of Professor Sir Cyril Burt, with whom he had a tumultuous professional relationship throughout his working life. (pp. 118–119).

Ahmed Hoosen Deedat (Arabic: احمد حسين ديدات; 1 July 1918 – 8 August 2005) was a South African writer and public speaker of Indian descent. He was best known as a Muslim missionary who held numerous inter-religious public debates with evangelical Christians, as well as video lectures, most of which centred around Islam, Christianity and the Bible. He also established the IPCI, an international Islamic missionary organisation, and wrote several booklets on Islam and Christianity which were widely distributed by the organisation. He was awarded the prestigious King Faisal International Prize in 1986 for his 50 years of missionary work. One focus of his work was providing Muslims with theological tools for defending themselves against active proselytising by Christian missionaries.^{[citation needed]} He used English to get his message across to Muslims and non-Muslims in the western world.

Ahmed Deedat was born in the town of Tadkeshwar, Surat, Bombay Presidency, British India in 1918. His father had emigrated to South Africa shortly after the birth of Ahmed Deedat. At the age of 9, Deedat left India to join his father in what is now known as Kwazulu-Natal. His mother died only a few months after his departure. Arriving in South Africa, Deedat applied himself with diligence to his studies, overcoming the language barrier and excelling in school, even getting promoted until he completed standard 6. However, due to financial circumstances, he had to quit school and start working by the time he was the age of 16.