Secundum quid (also called secundum quid et simpliciter, meaning "[what is true] in a certain respect and [what is true] absolutely") is a type of informal fallacy that occurs when the arguer fails to recognize the difference between rules of thumb (soft generalizations, heuristics that hold true as a general rule but leave room for exceptions) and categorical propositions, rules that hold true universally.
Since it ignores the limits, or qualifications, of rules of thumb, this fallacy is also named ignoring qualifications. The expression misuse of a principle can be used as well. [1]
Let me tell you: all great composers die young. Take Mendelssohn: he was 38. Or Mozart, just 35. And Schubert! Hundreds of songs, and he was only 31.
The arguer cites only the cases that support his point, conveniently omitting Bach, Beethoven, Brahms etc.
Water boils at a temperature of 212 °Fahrenheit; therefore boiling water will be hot enough to cook an egg hard in five minutes: but if we argue thus at an altitude of 5,000 feet, we shall be disappointed; for the height, through the difference in the pressure of the air, qualifies the truth of our general principle.
— H. W. B. Joseph
Compare with:
All men are mortal.
Socrates is a man.
Therefore, Socrates is mortal.
The following quatrain can be attributed to C. H. Talbot:
I talked in terms whose sense was hid,
Dividendo, componendo et secundum quid;
Now secundum quid is a wise remark
And it earned my reputation as a learned clerk.
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Instances of secundum quid are of two kinds:
A syllogism is a kind of logical argument that applies deductive reasoning to arrive at a conclusion based on two propositions that are asserted or assumed to be true.
A fallacy, also known as paralogia in modern psychology, is the use of invalid or otherwise faulty reasoning in the construction of an argument that may appear to be well-reasoned if unnoticed. The term was introduced in the Western intellectual tradition by the Aristotelian De Sophisticis Elenchis.
Deductive reasoning is the mental process of drawing deductive inferences. An inference is deductively valid if its conclusion follows logically from its premises, i.e. it is impossible for the premises to be true and the conclusion to be false.
The Summa Logicae is a textbook on logic by William of Ockham. It was written around 1323.
Special pleading is an informal fallacy wherein one cites something as an exception to a general or universal principle, without justifying the special exception. It is the application of a double standard.
A faulty generalization is an informal fallacy wherein a conclusion is drawn about all or many instances of a phenomenon on the basis of one or a few instances of that phenomenon. It is similar to a proof by example in mathematics. It is an example of jumping to conclusions. For example, one may generalize about all people or all members of a group from what one knows about just one or a few people:
Inferences are steps in reasoning, moving from premises to logical consequences; etymologically, the word infer means to "carry forward". Inference is theoretically traditionally divided into deduction and induction, a distinction that in Europe dates at least to Aristotle. Deduction is inference deriving logical conclusions from premises known or assumed to be true, with the laws of valid inference being studied in logic. Induction is inference from particular evidence to a universal conclusion. A third type of inference is sometimes distinguished, notably by Charles Sanders Peirce, contradistinguishing abduction from induction.
Inductive reasoning is a method of reasoning in which a general principle is derived from a body of observations. It consists of making broad generalizations based on specific observations. Inductive reasoning is distinct from deductive reasoning, where the conclusion of a deductive argument is certain given the premises are correct; in contrast, the truth of the conclusion of an inductive argument is probable, based upon the evidence given.
Logical reasoning is a mental activity that aims to arrive at a conclusion in a rigorous way. It happens in the form of inferences or arguments by starting from a set of premises and reasoning to a conclusion supported by these premises. The premises and the conclusion are propositions, i.e. true or false claims about what is the case. Together, they form an argument. Logical reasoning is norm-governed in the sense that it aims to formulate correct arguments that any rational person would find convincing. The main discipline studying logical reasoning is called logic.
A statistical syllogism is a non-deductive syllogism. It argues, using inductive reasoning, from a generalization true for the most part to a particular case.
The fallacy of accident is an informal fallacy and a deductively valid but unsound argument occurring in a statistical syllogism when an exception to a rule of thumb is ignored. It is one of the thirteen fallacies originally identified by Aristotle in Sophistical Refutations. The fallacy occurs when one attempts to apply a general rule to an irrelevant situation.
The fallacy of converse accident is an informal fallacy that can occur in a statistical syllogism when a rule that applies only to an exceptional case is wrongly applied to all cases in general.
Sophistical Refutations is a text in Aristotle's Organon in which he identified thirteen fallacies. According to Aristotle, this is the first work to treat the subject of deductive reasoning in ancient Greece.
In logic, logical form of a statement is a precisely-specified semantic version of that statement 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.
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 is generally considered to be a bad argument because the implicit (unstated) primary premise "What is natural is good" is typically irrelevant, having no cogent meaning in practice, or is an opinion instead of a fact.
A premise or premiss is a proposition—a true or false declarative statement—used in an argument to prove the truth of another proposition called the conclusion. Arguments consist of a set of premises and a conclusion.
An argument is a series of sentences, statements or propositions some of which are called premises and one is the conclusion. The purpose of an argument is to give reasons for one's conclusion via justification, explanation, and/or persuasion.
In logic, specifically in deductive reasoning, an argument is valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. It is not required for a valid argument to have premises that are actually true, but to have premises that, if they were true, would guarantee the truth of the argument's conclusion. Valid arguments must be clearly expressed by means of sentences called well-formed formulas.
Plausible reasoning is a method of deriving new conclusions from given known premises, a method different from the classical syllogistic argumentation methods of Aristotelian two-valued logic. The syllogistic style of argumentation is illustrated by the oft-quoted argument "All men are mortal, Socrates is a man, and therefore, Socrates is mortal." In contrast, consider the statement "if it is raining then it is cloudy." The only logical inference that one can draw from this is that "if it is not cloudy then it is not raining." But ordinary people in their everyday lives would conclude that "if it is not raining then being cloudy is less plausible," or "if it is cloudy then rain is more plausible." The unstated and unconsciously applied reasoning, arguably incorrect, that made people come to their conclusions is typical of plausible reasoning.
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