Supposition, Conditionals and Unstated Premises

E.P. Brandon


Informal logicians recognise the frequent use of unstated assumptions; some (e.g. Fisher) also recognise entertained arguments and recommend a suppositional approach (such as Mackie's) to conditional statements. It is here argued that these two be put together to make argument diagrams more accurate and subtle. Philosophical benefits also accrue: insights into Jackson's apparent violations of modus tollens and contraposition and McGee's counterexamples to the validity of modus ponens.


supposition, conditionals, unstated premises, argument analysis

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ISSN: 0824-2577