Arrange these norms in the order Kelsen's chain of validity ascends.

1. The individual norm in a judgment ordering a specific payment
2. The statutory article the judgment applies
3. The constitutional provision authorising that statute
4. The basic norm presupposed by legal thought

The last step is the one doing the philosophical work. Every other link derives its validity from the link above; the chain has to stop, and Kelsen stops it at a norm nobody issued, presupposed in order that the rest may be understood as valid. Hart's alternative is to stop at something observable instead: what officials actually treat as law.