[Zope] Check Security Permissions for a User?

hello, I played with the following code in a dtml-method to check if a user has a certain permission (e.g. "Manage Properties"): <dtml-var "_.SecurityGetUser().has_permission('Manage Properties',this())"> This results in 1 if the User has the permission or None if not... everything is fine so far. But when I do check for a nonexisting permission, like: <dtml-var "_.SecurityGetUser().has_permission('Really Unknown PermisionXXX',this())"> the result would be 1 too... What is the reason for this SecurityPolicy? Why not an exception? Or 0? thank you for advice Maik Jablonski.