Richard L. W. Clarke, Notes REASONING

Transcription

1 1 REASONING Reasoning is, broadly speaking, the cognitive process of establishing reasons to justify beliefs, conclusions, actions or feelings. It also refers, more specifically, to the act or process of using one's reason to derive one statement or assertion (the conclusion) from a prior group of statements or assertions (the premises) by means of a given method. There are at least five factors predicated of reasoning: 1. Universality: reasoning, when properly performed, is the same everywhere, that is, it does not vary from place to place (the reasoner s location does not matter); 2. Timelessness: reasoning, when properly performed, is always the same, that is, it does not vary from time to time (the era in which the reasoner lives does not matter); 3. Formalism: reasoning, when properly performed, consists of specific forms (e.g. the syllogism) the validity of which have stood the test of time; 4. Impersonality: the identity of the person reasoning (his or her gender, race, class, etc.) does not matter; 5. Objectivity: reasoning, when properly performed, leads to neutral, impartial knowledge, that is, objective knowledge. An argument is an attempt to demonstrate the validity of an assertion called a conclusion based on the truth of a set of assertions called premises. To put this another way, it is a set of premises (a justification) offered in support of a conclusion (a truth-claim or belief). It typically comprises a set of assumptions (the premises), a method of reasoning, and a conclusion. Etymologically-speaking, as Peter Caws has argued in an to the Philos-L list, the word 'argument' derives (on the mythological side) from Argus, the many-eyed and (on the philological side) from the Latin verb 'arguo,' which means 'to put in a clear light.' The main idea is of seeing clearly, getting clear about, throwing light on, and ideally that's what argument would be for. Formal argument aims for inferences of logical or mathematical clarity; in other cases it's more a matter of give and take in discussion, aiming for an agreement in which the parties come to see whatever it is in the same way, or to understand why they can't do so. A bad argument would be one that doesn't help in this way, and the worst would presumably be one that produces maximum obscurity rather than clarity. (Ibid) Argumentation is the socially situated, communicative practice by which humans can, do, and should reach conclusions through logical reasoning, that is, claims based on premises. It includes the arts and sciences of civil debate, dialogue, conversation, and persuasion. It studies rules of inference, logic, and procedural rules in both artificial and real world settings. In Fundamentals of Argumentation Theory: a Handbook of Historical Backgrounds and Contemporary Developments, Frans van Eemeren, Rob Grootendorst, and Snoeck Henkemans define argumentation as a verbal and social activity of reason aimed at increasing (or decreasing) the acceptability of a controversial standpoint for the listener or reader, by putting forward a constellation of propositions intended to justify (or refute) the standpoint before a rational judge. () A logical assertion is a statement that asserts or claims that a particular premise is valid.

2 2 A proposition is the content of an assertion, that is, it is true-or-false and defined by the meaning of a particular piece of language. The proposition is independent of the medium of communication with the result that different statements may communicate the same proposition. A logical argument is one in which the validity of the conclusion derives from a logical relationship that exists between the premises themselves, any intermediate assertions that may be present, and the conclusion. Implication or entailment refers to the relationship which exists between one proposition and another, whereas inference refers to the mental act or process of deriving a conclusion from prior premises and takes several forms. A valid argument does not presuppose that one's conclusion is necessarily true, that is, that it corresponds to reality. Validity is a property of the reasoning in the argument, not a property of the premises in the argument or the argument as a whole. In fact, the truth or falsity of the premises and the conclusion is irrelevant to the validity of the reasoning in the argument. An argument may be described as truth-preserving when, if the premises are true, the conclusion is accordingly also true. Alternatively, an argument may be fallacious, though not necessarily untrue. Formal fallacies occur when there is a problem with the form, or structure, of the argument. An informal fallacy is an error in reasoning that occurs due to a problem with the content, rather than mere structure, of the argument. Syllogisms A syllogism (Greek, [syllogismos] conclusion or inference) is a kind of logical argument in which one proposition (the conclusion) is inferred from two others (the premises) of a certain form. In his Prior Analytics, Aristotle defines syllogism as "a discourse in which, certain things having been supposed, something different from the things supposed results of necessity because these things are so" (24b18 20). Syllogisms take two main forms: Deduction refers to the process of reasoning in which an assertion concerning some particular fact (the conclusion) is necessitated by, or derived from, or entailled by previously known facts of a more general nature (the premises). In other words, if the premises are true, the conclusion must be true. In traditional Aristotelian logic, deductive reasoning is inference in which the conclusion is of lesser or equal generality than the premises, as opposed to inductive reasoning, where the conclusion is of greater generality than the premises. Other theories of logic define deductive reasoning as inference in which the conclusion is just as certain as the premises, as opposed to inductive reasoning, where the conclusion can have less certainty than the premises. In both approaches, the conclusion of a deductive inference is necessitated by the premises: the premises can't be true while the conclusion is false. (In Aristotelian logic, the premises in inductive reasoning can also be related in this way to the conclusion.) Examples: Valid: Premise 1: All humans are mortal. Premise 2: Socrates is a human. Conclusion: Socrates is mortal. Or: Premise 1: The picture is above the desk. Premise 2: The desk is above the floor. Conclusion: Therefore the picture is above the floor. Invalid:

3 3 Premise 1: Every criminal opposes the government. Premise 2: Everyone in the opposition party opposes the government. Premise 3: Therefore everyone in the opposition party is a criminal. This is invalid because the premises fail to establish commonality between membership in the opposition party and being a criminal. This is the famous fallacy of undistributed middle. An enthymeme (Greek:, enthum ma), in its modern sense, is an informally stated syllogism (a three-part deductive argument) with an unstated assumption that must be true for the premises to lead to the conclusion. In an enthymeme, part of the argument is missing because it is assumed. In a broader usage, the term enthymeme is sometimes used to describe an incomplete argument of forms other than the syllogism. For Aristotle, who defined it in his Rhetoric, an enthymeme was a "rhetorical syllogism" based on probable opinions and, as such, to be distinguished from a scientific syllogism. It is aimed at persuasion while scientific syllogism is aimed at demonstration. An example of an enthymeme is Socrates is mortal because he is human. Induction is the process of reasoning in which the particular premises of an argument are believed to support a conclusion of a general nature but do not ensure it (e.g. the specific proposition 'this ice is cold' is used to infer that 'all ice is cold'). It is to ascribe properties or relations to types based on limited observations of particular tokens; or to formulate laws based on limited observations of recurring phenomenal patterns. Even in the best, or strongest, cases of inductive reasoning, the truth of the premises does not guarantee the truth of the conclusion. Instead, the conclusion of an inductive argument follows with some degree of probability. In addition, the conclusion of an inductive argument contains more information than is already contained in the premises. Thus, this method of reasoning is ampliative. For example, Premise: The sun has risen in the east every morning up until now. Conclusion: The sun will also rise in the east tomorrow. Or: Premise: A billiard ball moves when struck with a cue. Conclusion: For every action, there is an equal and opposite re-action. Abduction (or inference to the best explanation) is a method of reasoning, employed in the sciences especially, in which one chooses which hypothesis would, if true, best explain the relevant evidence. It is the reasoning process that starts from a set of observed facts and derives their most likely explanations. What separates abduction from the other forms of reasoning is an attempt to favour one conclusion above others, by attempting to falsify alternative explanations or by demonstrating the likelihood of the favored conclusion, given a set of more or less disputable assumptions. Though it often involves both inductive and deductive arguments, because the conclusion in an abductive argument does not follow with certainty from its premises it is best thought of as a form of inductive reasoning. Argument by Analogy, also a form of inductive reasoning, is an inference from one particular to another particular. It normally takes the following form: A has characteristics x, y, and z B has characteristics x and y

4 4 So, B has (or probably has) characteristic z Reasoning by analogy goes from one particular thing, or category, to another particular thing, or category. As with other forms of inductive argument, even the best reasoning in an argument from analogy can only make the conclusion probable, given the truth of the premises, not certain. Other forms of reasoning include: Dialectic (from the Greek, dialetik ) is a form of reasoning based on an exchange of propositions (theses) and counter-propositions (antitheses) resulting in either the refutation of one of the points of view expressed, or a synthesis of the opposing assertions, or at least a qualitative transformation in the direction of the dialogue. It usually takes the form of a dialogue between two or more people who may hold differing views, yet wish to pursue truth by seeking agreement with one another. Fields of Study Argumentation Theory conceives of reasoning as a socially-situated, communicative practice and accordingly studies the credibility of arguments by identifying the premises, conclusions, and fallacies found in various types of communication that occur in every day, practical, real-life situations. Critical Thinking refers to the general process of analyzing or evaluating information, particularly statements or propositions that people have offered as true, by reflecting on the meaning of statements, studying the process of reasoning, examining the offered evidence, and evaluating the judgments proposed in this way. Ralph Johnson defines critical thinking as the evaluation of an intellectual product (an argument, an explanation, a theory) in terms of its strengths and weaknesses. Logic (from the Classical Greek [logos], originally meaning the word or what is spoken and later thought or reason), is the branch of philosophy devoted to the study of arguments, to be precise, the study of patterns found in reasoning and criteria for the evaluation of arguments. More precisely, logic studies the laws of valid inference. The task of the logician is to advance an account of valid and fallacious inference to allow one to distinguish logical from flawed arguments. In short, logicians take arguments apart and study their structure in more detail than a cursory glance would otherwise allow. Formal logic seeks to compare the form of a particular argument with one of the forms of proper inference (that is, whereby the conclusion can be derived from the premises using accepted rules of derivation, or by some other formal method). Informal Logic is defined by Ralph Johnson and J. Anthony Blair as a branch of logic whose task is to develop non-formal standards, criteria, procedures for the analysis, interpretation, evaluation, criticism and construction of argumentation ("The Current State of Informal Logic," Informal Logic (1987): ). Informal Logic, which studies inference without formalizing it to any (great) extent, is thought to be a synonym for Argumentation Theory. In general, the label 'argumentation' is used by speech and communication scholars while the label 'informal logic' is used by philosophers. Philosophical Logic is the application of formal logical techniques to philosophical problems. In the UK, according to Anthony Grayling, philosophical logic is the attempt to

5 5 solve general philosophical problems that arise when we use or think about formal logic: problems about existence, necessity, analyticity, a prioricity, propositions, identity, predication, truth. Philosophy of Logic: is concerned with the nature and justification of systems of logic, dealing with questions such as whether there exists only a single logic or whether there are many logics.