A being that cannot understand at all is at least protected from _mis_-understandings. But beings that get knowledge by means of inferring and interpreting, by judging what things signify in relation to one another, are constantly exposed to the danger of _mis_-apprehension, _mis_-understanding, _mis_-taking--taking a thing amiss. A constant source of misunderstanding and mistake is indefiniteness of meaning. Through vagueness of meaning we misunderstand other people, things, and ourselves; through its ambiguity we distort and pervert. Conscious distortion of meaning may be enjoyed as nonsense; erroneous meanings, if clear-cut, may be followed up and got rid of. But vague meanings are too gelatinous to offer matter for analysis, and too pulpy to afford support to other beliefs. They evade testing and responsibility. Vagueness disguises the unconscious mixing together of different meanings, and facilitates the substitution of one meaning for another, and covers up the failure to have any precise meaning at all. It is the aboriginal logical sin--the source from which flow most bad intellectual consequences. Totally to eliminate indefiniteness is impossible; to reduce it in extent and in force requires sincerity and vigor. To be clear or perspicuous a meaning must be detached, single, self-contained, homogeneous as it were, throughout. The technical name for any meaning which is thus individualized is _intension_. The process of arriving at such units of meaning (and of stating them when reached) is _definition_. The intension of the terms _man_, _river_, _seed_, _honesty_, _capital_, _supreme court_, is the meaning that _exclusively_ and _characteristically_ attaches to those terms. This meaning is set forth in the definitions of those words. The test of the distinctness of a meaning is that it shall successfully mark off a group of things that exemplify the meaning from other groups, especially of those objects that convey nearly allied meanings. The river-meaning (or character) must serve to _designate_ the Rhone, the Rhine, the Mississippi, the Hudson, the Wabash, in spite of their varieties of place, length, quality of water; and must be such as _not_ to suggest ocean currents, ponds, or brooks. This use of a meaning to mark off and group together a variety of distinct existences constitutes its _extension_. [Sidenote: Definition and division]