Full Idea
If there is such a notion as 'absolute necessity', its logic is surely S5.
Clarification
S5 is the most 'universal' system of modal logic
Gist of Idea
'Absolute necessity' would have to rest on S5
Source
Ian Rumfitt (The Boundary Stones of Thought [2015], 3.3)
Book Reference
Rumfitt,Ian: 'The Boundary Stones of Thought' [OUP 2015], p.76
A Reaction
There are plenty of people (mainly in the strict empiricist tradition) who don't believe in 'absolute' necessity.