<Dd> Therefore, Tweedy (probably) flies . </Dd> <P> This argument is reasonable and the premises support the conclusion unless additional information indicating that the case is an exception comes in . If Tweedy is a penguin, the inference is no longer justified by the premise . Defeasible arguments are based on generalizations that hold only in the majority of cases, but are subject to exceptions and defaults . In order to represent and assess defeasible reasoning, it is necessary to combine the logical rules (governing the acceptance of a conclusion based on the acceptance of its premises) with rules of material inference, governing how a premise can support a given conclusion (whether it is reasonable or not to draw a specific conclusion from a specific description of a state of affairs). Argumentation schemes have been developed to describe and assess the acceptability or the fallaciousness of defeasible arguments . Argumentation schemes are stereotypical patterns of inference, combining semantic - ontological relations with types of reasoning and logical axioms and representing the abstract structure of the most common types of natural arguments . The argumentation schemes provided in (Walton, Reed & Macagno, 2008) describe tentatively the patterns of the most typical arguments . However, the two levels of abstraction are not distinguished . For this reason, under the label of "argumentation schemes" fall indistinctly patterns of reasoning such as the abductive, analogical, or inductive ones, and types of argument such as the ones from classification or cause to effect . A typical example is the argument from expert opinion, which has two premises and a conclusion . </P> <Table> <Tr> <Td> Major Premise: </Td> <Td> Source E is an expert in subject domain S containing proposition A . </Td> </Tr> <Tr> <Td> Minor Premise: </Td> <Td> E asserts that proposition A is true (false). </Td> </Tr> <Tr> <Td> Conclusion: </Td> <Td> A is true (false). </Td> </Tr> </Table> <Tr> <Td> Major Premise: </Td> <Td> Source E is an expert in subject domain S containing proposition A . </Td> </Tr>

4 types of support that can be used as grounds