The Rev. Harry Emerson Fosdick will speak at 7.30 o'clock tonight in the Living Room of the Union on the subject, "What is Christianity?" The meeting will be open to all students of the University whether members of the Union or not. W. H. Trumbull '15, representing the Joint Executive Committee of Phillips Brooks House will preside.

Dr. Fosdick is well known to Harvard audiences. At yesterday's service in Appleton Chapel, which he conducted, every seat and all available standing room was occupied. Even so, many who wished to hear him speak were unable to gain entrance. He spoke last May at the Union on the subject, "Is Religion Coming Back?" The preceding year at Phillips Brooks House he discussed "The Ministry as a Vocation." He is professor of practical theology at the Union Theological Seminary and also pastor of the Fifth Avenue Presbyterian Church of New York.

Has Written Many Noted Books

In addition to a national reputation as a speaker Dr. Fosdick has won considerable prominence as the author of several books on practical theology. His works include "The Manhood of the Master," "The Meaning of Prayer," "The Meaning of Faith," and "The Meaning of Service."