"Though the First Amendment does not define freedom of religion, freedom of speech, freedom of the press, and the right of assembly, it does provide the basis for later definitions. It is these definitions that have come to be grouped under the category of intellectual freedom -- the unrestriced ability to think or reason as we wish and to express our ideas.
Source: Harer, J. B. (1992). Intellectual Freedom: a Reference Handbook (p. 1). Santa Barbara, CA: ABC-CLIO, Inc.
David McCullough, the Pulitzer Prize-winning historian
and author of 1776, discusses intellectual freedom.