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The logical form of this argument is known as modus ponens, [39] which is a classically valid form. [40] So, in classical logic, the argument is valid, although it may or may not be sound, depending on the meteorological facts in a given context. This example argument will be reused when explaining § Formalization.
Aristotelian propositions take forms like "All men are mortal" and "Socrates is a man." Aristotelian logic identifies a categorical proposition as a sentence which affirms or denies a predicate of a subject, optionally with the help of a copula. An Aristotelian proposition may take the form of "All men are mortal" or "Socrates is a man."
In order to evaluate these forms, statements are put into logical form. Logical form replaces any sentences or ideas with letters to remove any bias from content and allow one to evaluate the argument without any bias due to its subject matter. [1] Being a valid argument does not necessarily mean the conclusion will be true. It is valid because ...
It differs in this aspect from propositional logic, in which any two propositions can be linked using a logical connective like "and" to form a new complex proposition. [ 109 ] The square of opposition is often used to visualize the relations between the four basic categorical propositions in Aristotelian logic.
Modus ponens is a mixed hypothetical syllogism and is closely related to another valid form of argument, modus tollens. Both have apparently similar but invalid forms: affirming the consequent and denying the antecedent. Constructive dilemma is the disjunctive version of modus ponens. The history of modus ponens goes back to antiquity. [4]
logical structure See logical form. logical theorem A proposition that has been proven to be true within a specific system of logic, based on the system's axioms and inference rules. logical truth A statement that is true in all possible worlds or under all possible interpretations, due to its logical form rather than the content of its terms.
For example, a tsunami could also explain why the streets are wet but this is usually not the best explanation. As a form of non-deductive reasoning, abduction does not guarantee the truth of the conclusion even if the premises are true. [80] [82] The more plausible the explanation is, the stronger it is supported by the premises.
A standard view is that whether an argument is valid is a matter of the argument's logical form. Many techniques are employed by logicians to represent an argument's logical form. A simple example, applied to two of the above illustrations, is the following: Let the letters 'P', 'Q', and 'S' stand, respectively, for the set of men, the set of ...