These elements include data, claim, warrants, qualifiers, rebuttals. Stephen Toulmin, originally a British logician, is now a professor at USC. He became frustrated with the inability of formal logic to explain everyday arguments, which prompted him to develop his own model of practical reasoning. evidence: facts, statistics, reports, or physical proof, source credibility: authorities, experts, celebrity endorsers, a close friend, or someone's say-so analysis and reasoning: reasons may be offered as proof Warrants/General Strategies of Argument Warrants are chains of reasoning that connect the claim and evidence/reason. A warrant is the principle, provision or chain of reasoning that connects the grounds/reason to the claim. Warrants operate at a higher level of generality than a claim or reason, and they are not normally explicit.