Button isEnabled method requiring a boolean responds unexpectedly

[Jim Short]

T works, True does not
F works, and so does False and Nil

Why not True?

[owenwengerd]

It depends what True is set to. You could (setq True 'T), then it will work, otherwise the symbol True will be NIL.

[Jim Short]

Since T is true by lisp and True is just an undefined symbol evaluating to nil unless otherwise set.

Any an symbol evaluating to nil would serve as false.

Best to use t and nil.

Thanks,
Jim