apodeictic

adjective3

1. •
   Incontrovertible; demonstrably true or certain.
2. •
   Of the characteristic feature of a proposition that is necessary (or impossible): perfectly certain (or inconceivable) or incontrovertibly true (or false); self-evident.

   • Descartes sought certainty in the existence of God grounded in apodeictic demonstrations. — 2009
3. •
   Affording proof; demonstrative.