Under Cayley–Dickson constructions, the sedenions 
  
    
      
        
          S
        
      
    
    {\displaystyle \mathbb {S} }
   constitute a further fourth extension over 
  
    
      
        
          R
        
      
    
    {\displaystyle \mathbb {R} }
  . The real numbers are ordered, commutative and associative algebras, as well as alternative algebras with power-associativity.
Boyd held that his decision cycle has philosophical generality, though for strategists the point remains that, through swift decisions, one can disrupt an opponents decision cycle. Richard McKeon outlined four classes (each with four subclasses) of modes of philosophical inquiry: (1) Modes of Being (Being); (2) Modes of Thought (That which is); (3) Modes of Fact (Existence); (4) Modes of Simplicity (Experience)—and, corresponding to them, four classes (each with four subclasses) of philosophical semantics: Principles, Methods, Interpretations, and Selections. (See McKeons "Philosophic Semantics and Philosophic Inquiry" in Freedom and History and Other Essays, 1989.) Jonathan Lowe (E.J. Lowe) argues in The Four-Category Ontology, 2006, for four categories: kinds (substantial universals), attributes (relational universals and property-universals), objects (substantial particulars), and modes (relational particulars and property-particulars, also known as "tropes"). (See Lowes "Recent Advances in Metaphysics," 2001, Eprint)
Four opposed camps of the morality and nature of evil: moral absolutism, amoralism, moral relativism, and moral universalism. In technology
The resin identification code used in recycling to identify low-density polyethylene. Most furniture has four legs – tables, chairs, etc. The four color process (CMYK) is used for printing. Wide use of rectangles (with four angles and four sides) because they have effective form and capability for close adjacency to each other (houses, rooms, tables, bricks, sheets of paper, screens, film frames). In the Rich Text Format specification, language code 4 is for the Chinese language. Codes for regional variants of Chinese are congruent to 4 mod 256.
Credit card machines have four-twelve function keys.