Benjamin Samuel Bloom (February 21, 1913 – September 13, 1999) was an American educational psychologist who made contributions to the classification of educational objectives and to the theory of mastery learning. He is particularly noted for leading educational psychologists to develop the comprehensive system of describing and assessing educational outcomes in the mid-1950s.[1] He has influenced the practices and philosophies of educators around the world from the latter part of the twentieth century.