Logic of Causality
Sufficient & Necessary Conditions:
Definition
Sufficient Condition

if that Condition is present
(*), the Phenomenon will be present (*)
Necessary Condition

if the Phenomenon is present
(*), that Condition will be present (*)
Sufficient & Necessary
Conditions: Eliminating Candidates
When a Condition is not Sufficient

presence (*) of C and absence ()
of P falsifies "if C, then
P"

therefore, when C is present (*)
and P is absent (), that condition is not a sufficient cause (C is ~S)
When a Condition is not Necessary

presence (*) of P and absence ()
of C falsifies "if P, then
C"

therefore, when P is present (*)
and C is absent (), that condition is not a necessary cause (C is ~N)
GAY Method for
Calculating Sufficient and Necessary
Conditions
Condition 
Phenomenon 
Causal Status 
* 
 
C is ~S 
 
* 
C is ~N 
 
 
C is S, given this data 
* 
* 
C is N, given this data 