Interpreted on a casual basis, the set X can be treated as a list of "boolean variables", or, according to another reading, as a list of "boolean variable names", but both of these choices are subject to the eventual requirement of saying exactly what a "variable" is. | Interpreted on a casual basis, the set X can be treated as a list of "boolean variables", or, according to another reading, as a list of "boolean variable names", but both of these choices are subject to the eventual requirement of saying exactly what a "variable" is. |