As discussed extensively in Section 1 (pp. 1.3:15-35), measurement processes, including ordinal measurement, are applicable only to units that are commensurable, i. e., similar in kind with respect to the attribute being measured. The idea of "teleological measurement," by which an individual weighs either a material or a spiritual value "against the hierarchy of all his other goals, desires and needs," is explored by Ayn Rand in her Introduction to Objectivist Epistemology (New York: New American Library, 1979), pp. 42-5 (more information).