What is the central idea behind Kelsen's distinction between 'is' (Sein) and 'ought' (Sollen) in his Pure Theory of Law?
1
'Is' refers to laws enforced by the State, while 'ought' refers to moral obligations.
2
'Is' refers to facts or events in the natural world, while 'ought' refers to legal norms.
3
'Is' refers to statutory laws, while 'ought' refers to customary laws.
4
'Is' refers to judicial decisions, while 'ought' refers to laws made by the legislature.