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How are dependent (or linked) premises to be distinguished from independent (or convergent) premises? Deductive validity, sometimes proposed as a necessary condition for depende'nce, cannot be, for the premises of both inductive and deductive but invalid arguments can be dependent. The question is really this: When do multiple premises for a certain conclusion fonn one argument for that conclusion and when do they form multiple arguments? Answer: Premises are dependent when the evidence they offer for their conclusion is more than (...) the ordinary sum of their probabilities. Ordinary sums are defined in the paper. (shrink)

This definitive survey of the hottest issues in inductive logic sets the stage for further classroom discussion.

Sometimes logical support for a conclusion is provided exclusively by premises which are independently relevant to that conclusion. At other times, support is provided exclusively by independently irrelevant premises. On still other occasions, relevant and irrelevant premises may collectively offer a distinctive pattern of support. This paper provides a rigorous account of some of these differences in terms of a tripartite classification of convergent, linked and hybrid arguments. These various arguments are defined, diagrammed, and some of their logical properties are (...) explored. (shrink)

Quantitative apparatus for assessing strength of an argument was improved in the article. A probative generalisation and verification of the R.Yanal's algorithm to calculate convergent argument were proposed. The generalization obtained deals with both quantity (or number) and quality (or truth-values) of the argument's reasons.

Most recent writers of informal logic texts draw a distinction between "linked" and "convergent" arguments. According to its inventor, Stephen Thomas, the distinction is of the utmost importance; it "seems crucial to the analysis and evaluation of reasoning in natural language." I argue that the distinction has not been drawn in any way that makes it both clear and of any real originality or importance. Many formulations are obscure or conceptually incoherent. One formulation of the distinction does seem tolerably clear (...) and I develop another, but neither promises to make it matter much. We can well do without it. (shrink)