One in a series of instructional units designed for gifted students, this booklet describes a humanities unit for students in middle and secondary grades. The specific focus of the unit is on truth as it is perceived and expressed in philosophy, literature, art, music, drama, and the social sciences. The study of truth and its surrounding concepts will enable the student to examine the relationship between the operation of "outer space" (i.e., the world outside the human mind) and the concept of "inner space" (the world within a person's mind). Further, the unit introduces the fields of epistemology and structured critical thinking. Seventeen suggested activities (such as role playing a skeptic or a liar and examining television advertising) are followed by a list of suggested readings (philosophy and other textbooks, novels, short stories, poetry, and drama), and by a listing of suggested audio-visual material. (CL)