Structural rule A famous structural rule is known as cut. Considerable effort is spent by proof theorists in showing that cut rules are superfluous in various logics. More precisely, what is shown is that cut is only (in a sense) a tool for abbreviating proofs, and does not add to the theorems that can be proved. The successful 'removal' of cut rules, known as "cut elimination", is directly related to the philosophy of "computation as normalization" (see Curry–Howard correspondence); it often gives a good indication of the complexity of deciding a given logic. Structural rule In proof theory, a structural rule is
Five-second rule Five-second rule The five-second rule, sometimes also the three-second rule, is a western cultural food hygiene concept, that states that there is a defined window where it is permissible to pick up food (or sometimes cutlery) after it has been dropped and thus exposed to contamination. Some may believe this assertion, whereas most people employ the rule as an amusing social fiction that allows them to eat a dropped piece of food, despite the potential reservations of their peers. How many and what type of bacteria would stick to a piece of dropped food depends on many factors, the food