What chiefly distinguishes persuasive reasoning from a demonstrative proof?

Proof of Mutual Hindrance: Divine Unity, Conflicting Wills and Eternity of Attributes

• A demonstration entails its conclusion; persuasion may appeal to accepted premises
• Demonstration relies only on acceptance, persuasion on strict entailment
• The difference depends solely on argument length
• Persuasion and demonstration always yield contradictory conclusions