Strength (mathematical logic)

The relative strength of two systems of formal logic can be defined via model theory. Specifically, a logic ${\displaystyle \alpha }$ is said to be as strong as a logic ${\displaystyle \beta }$ if every elementary class in ${\displaystyle \beta }$ is an elementary class in ${\displaystyle \alpha }$.^[1]

See also

• Abstract logic
• Lindström's theorem