These sentences gain acceptance on different grounds:
1. “Adding equal quantities to equal quantities preserves equality”: a basic mathematical principle once the terms are fixed.
2. “Our opponent has explicitly conceded this principle”: a dialectical concession within a dispute.
3. “Experienced specialists recommend this practice”: an accepted report relying on the authority of those specialists.
They illustrate demonstrative material, a dialectical concession, and a rhetorical accepted premise. Classification depends on why the claim is accepted as well as what it states.