Before we can proceed to a formal definition of conflict we must examine another concept, that of behavior space. The position of a behavior unit at a moment of time is defined by a set of values (subset, to be technical) of a set of variables that defines the behavior unit. These variables need not be continuous or quantitatively measurable. The different values of a variable must, however, be capable of simple ordering; that is, of any two values it must be possible to say that one is 'after' (higher, lefter, brighter than) the other.

p. 3 - Conflict and defense: A general theory, 1962