|Non-Aristotelian logic; specifically, Alfred Korzybski's General Semantics. Its multivalued rather'n two-valued, hence much better suited for showing off the hero's mental agility. Van Vogt popularized Korzybski's doctrines in one of his more impressive save-the-world-with-a-gimmick sagas, the World of Null-A -- Players of Null-A series [symbol A with line above it read "null-A"], tho the chief null-A discipline practiced by hero Gosseyn is not mentioned by Korzybski: the cortico-thalamic pause, in which the rational cortex is "integrated" into control of the emotional thalamus, whereat semantically clever words sound forth. (Wrai Ballard was often disappointed when Gosseyn performed this maneuver; he kept expecting somebody to clout G over the head in the middle of it. Nobody ever did.) As you'd expect in a pulpyarn, however, the hero wins not by application of philosophic principles but -- in this case -- by developing the double brain (a group of nervelike cells, not a second thinking mind) he possesses to such a point that it can be used to control matter and energy and goshwow (also).