Dr. Schaeffer was a Christian theologian and philosopher who, together with his wife Edith, founded the first L'Abri community in Switzerland in 1955. From the 1960's, until his death in 1984. Dr Schaeffer's lectures and discussions were recorded as a resource for future students.

http://www.labri-ideas-library.org/index.asp

For forty years Ravi Zacharias has spoken all over the world and in numerous universities, notably Harvard, Princeton, and Oxford University.  He has addressed writers of the peace accord in South Africa, the president’s cabinet and parliament in Peru, and military officers at the Lenin Military Academy and the Center for Geopolitical Strategy in Moscow.  At the invitation of the President of Nigeria, he addressed delegates at the First Annual Prayer Breakfast for African Leaders held in Mozambique.

 

Check out his website. Ravi is a fresh a fresh air in the church of today. His logical thinking and understanding of the Scriptures, science, and the human mind enables him to help skeptics and non-believers to see a life of faith from a different perspective.

http://www.rzim.org/about/ravi-zacharias/