Ad hominem, short for argumentum ad hominem, is a fallacious argumentative strategy whereby genuine discussion of the topic at hand is avoided by instead attacking the character, motive, or other attribute of the person making the argument, or persons associated with the argument, rather than attacking the substance of the argument itself. The terms ad mulierem and ad feminam have been used specifically when the person receiving the criticism is female.
A slippery slope argument (SSA), in logic, critical thinking, political rhetoric, and caselaw, is a consequentialist logical device in which a party asserts that a relatively small first step leads to a chain of related events culminating in some significant effect. The core of the slippery slope argument is that a specific decision under debate is likely to result in unintended consequences. The strength of such an argument depends on the warrant, i.e. whether or not one can demonstrate a process that leads to the significant effect. This type of argument is sometimes used as a form of fearmongering, in which the probable consequences of a given action are exaggerated in an attempt to scare the audience. The fallacious sense of "slippery slope" is often used synonymously with continuum fallacy, in that it ignores the possibility of middle ground and assumes a discrete transition from category A to category B. In a non-fallacious sense, including use as a legal principle, a middle-ground possibility is acknowledged, and reasoning is provided for the likelihood of the predicted outcome.
A fallacy is the use of invalid or otherwise faulty reasoning, or "wrong moves" in the construction of an argument. A fallacious argument may be deceptive by appearing to be better than it really is. Some fallacies are committed intentionally to manipulate or persuade by deception, while others are committed unintentionally due to carelessness or ignorance. The soundness of legal arguments depends on the context in which the arguments are made.
Circular reasoning is a logical fallacy in which the reasoner begins with what they are trying to end with. The components of a circular argument are often logically valid because if the premises are true, the conclusion must be true. Circular reasoning is not a formal logical fallacy but a pragmatic defect in an argument whereby the premises are just as much in need of proof or evidence as the conclusion, and as a consequence the argument fails to persuade. Other ways to express this are that there is no reason to accept the premises unless one already believes the conclusion, or that the premises provide no independent ground or evidence for the conclusion. Begging the question is closely related to circular reasoning, and in modern usage the two generally refer to the same thing.
Trivial objections is an informal logical fallacy where irrelevant and sometimes frivolous objections are made to divert the attention away from the topic that is being discussed. This type of argument is called a "quibble" or "quillet". Trivial objections are a special case of red herring.
Argumentation theory, or argumentation, is the interdisciplinary study of how conclusions can be reached through logical reasoning; that is, claims based, soundly or not, 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 philosophy and mathematics, a logical form of a syntactic expression is a precisely-specified semantic version of that expression in a formal system. Informally, the logical form attempts to formalize a possibly ambiguous statement into a statement with a precise, unambiguous logical interpretation with respect to a formal system. In an ideal formal language, the meaning of a logical form can be determined unambiguously from syntax alone. Logical forms are semantic, not syntactic constructs; therefore, there may be more than one string that represents the same logical form in a given language.
In philosophy, a formal fallacy, deductive fallacy, logical fallacy or non sequitur is a pattern of reasoning rendered invalid by a flaw in its logical structure that can neatly be expressed in a standard logic system, for example propositional logic. It is defined as a deductive argument that is invalid. The argument itself could have true premises, but still have a false conclusion. Thus, a formal fallacy is a fallacy where deduction goes wrong, and is no longer a logical process. However, this may not affect the truth of the conclusion since validity and truth are separate in formal logic.
An appeal to nature is an argument or rhetorical tactic in which it is proposed that "a thing is good because it is 'natural', or bad because it is 'unnatural'". It can be a bad argument, because the implicit (unstated) primary premise "What is natural is good" typically is irrelevant, having no cogent meaning in practice, or is an opinion instead of a fact. In some philosophical frameworks where natural and good are clearly defined in a specific context, the appeal to nature might be valid and cogent.
Douglas Neil Walton is a Canadian academic and author, known for his books and papers on argumentation, logical fallacies and informal logic. He is presently Distinguished Research Fellow of the Centre for Research in Reasoning, Argumentation, and Rhetoric (CRRAR) at the University of Windsor, Ontario, Canada, and before that (2008–14), he held the Assumption Chair of Argumentation Studies at the University of Windsor. Walton’s work has been used to better prepare legal arguments and to help develop artificial intelligence.
In informal logic and philosophy, an argument map or argument diagram is a visual representation of the structure of an argument. An argument map typically includes the key components of the argument, traditionally called the conclusion and the premises, also called contention and reasons. Argument maps can also show co-premises, objections, counterarguments, rebuttals, and lemmas. There are different styles of argument map but they are often functionally equivalent and represent an argument's individual claims and the relationships between them.
In informal logic and argument mapping, a lemma is simultaneously a contention for premises below it and a premise for a contention above it. Transitivity: If one has proof that B follows from A and proof that C follows from B, then one has proof that C follows from A.
A co-premise is a premise in reasoning and informal logic which is not the main supporting reason for a contention or a lemma, but is logically necessary to ensure the validity of an argument. One premise by itself, or a group of co-premises can form a reason.
In both formal and informal logic, a main contention or conclusion is a thought which can be either true or false and is usually the most controversial proposition being argued for. In reasoning, a main contention is represented by the top of an argument map, with all supporting and objecting premises which bear upon it placed underneath.
In logic and philosophy, an argument is a series of statements, called the premises or premisses, intended to determine the degree of truth of another statement, the conclusion. The logical form of an argument in a natural language can be represented in a symbolic formal language, and independently of natural language formally defined "arguments" can be made in math and computer science.
Informal logic, intuitively, refers to the principles of logic and logical thought outside of a formal setting. However, perhaps because of the "informal" in the title, the precise definition of "informal logic" is a matter of some dispute. Ralph H. Johnson and J. Anthony Blair define informal logic 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." This definition reflects what had been implicit in their practice and what others were doing in their informal logic texts.
Ralph Henry Johnson is a Canadian American philosopher, born in Detroit, Michigan. Johnson has been credited as one of the founding members of the informal logic movement in North America, along with J. Anthony Blair who co-published one of the movement's most influential texts, "Logical Self-Defense," with Johnson. Alongside its founder, Blair, Johnson co-directed the Centre for Research in Reasoning, Argumentation, and Rhetoric at the University of Windsor. As Johnson and Blair write in the preface to the newest edition of Logical Self-Defense on the influential nature of the text:
"We might note that the theoretical perspective introduced in Logical Self-Defense has proved quite influential among textbook authors. It is to be found in modified form in A Practical Study of Argument by Trudy Govier, in Attacking Faulty Reasoning by T. Edward Damer, in Logic in Everyday Life and Open Minds and Everyday Reasoning by Zachary Seech, in Thinking Logically by James B. Freeman, and in Good Reasoning Matters by Leo Groarke and Christopher W. Tindale."
Logic is the systematic study of the form of valid inference, and the most general laws of truth. A valid inference is one where there is a specific relation of logical support between the assumptions of the inference and its conclusion. In ordinary discourse, inferences may be signified by words such as therefore, hence, ergo, and so on.
