Informal Logical Fallacies  

Oleh:

Risen, Jane L. ; Gilovich, Thomas

Jenis: Article from Books - E-Book
Dalam koleksi: Critical Thinking in Psychology, page 110-130.
Topik: Fallacies of Evidence Search and Interpretation; Fallacies of Inference; Avoiding Informal Logical Fallacies
Fulltext: Informal Logical Fallacies.pdf (138.21KB)

Isi artikel

Is this a valid conclusion? According to formal logic, it is. Formally, an argument is valid if the conclusion follows from the premises (whether or not the premises are true) and is invalid if it does not. Thus, formal logic is only concerned with the rules for drawing conclusions from a given set of premises (Baron, 1994). It does not specify a standard for evaluating the premises themselves (except, of course, to the extent that the premises were derived as conclusions from other premises). This chapter focuses on informal logic. Unlike formal logic, informal logic seeks standards for the generation and evaluation of premises. Thus, if Premise 1 is not supported by suf?cient evidence, then, according to informal logic, the conclusion about the chapter is not valid. So don’t despair: This chapter may have more promise than our opening syllogism would compel you to conclude. A second difference between formal logic and informal logic is that formal logic deals with certainty, and therefore does not offer a way to weigh the reasonableness of multiple valid or invalid conclusions (Baron, 1994). For instance, if the ?rst premise were, “Some good chapters begin with pithy quotes,” the conclusion would be invalid. The conclusion would also be invalid if the ?rst premise read, “Almost every good chapter begins with apithy quote.” The conclusion surely seems more reasonable in the latter case than in the former, but formal logic deems them equally invalid. Formal logic has the desirable properties of objectivity and precision. And although some of that objectivity and precision is lost with informal logic, much is gained in applicability and utility.

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