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The corresponding conditional of a valid argument is a logical truth and the negation of its corresponding conditional is a contradiction. The conclusion is a necessary consequence of its premises. An argument that is not valid is said to be "invalid". An example of a valid (and sound) argument is given by the following well-known syllogism:
A central concern in logic is whether a deductive inference is valid or not. Validity is often defined in terms of necessity, i.e. an inference is valid if and only if it is impossible for the premises to be true and the conclusion to be false. Incorrect inferences and arguments, on the other hand, fail to support their conclusion.
The types of logical reasoning differ concerning the exact norms they use as well as the certainty of the conclusion they arrive at. [1] [15] Deductive reasoning offers the strongest support and implies its conclusion with certainty, like mathematical proofs. For non-deductive reasoning, the premises make the conclusion more likely but do not ...
For valid arguments, the logical structure of the premises and the conclusion follows a pattern called a rule of inference. [12] For example, modus ponens is a rule of inference according to which all arguments of the form "(1) p , (2) if p then q , (3) therefore q " are valid, independent of what the terms p and q stand for. [ 13 ]
As the study of argument is of clear importance to the reasons that we hold things to be true, logic is of essential importance to rationality. Arguments may be logical if they are "conducted or assessed according to strict principles of validity", [1] while they are rational according to the broader requirement that they are based on reason and knowledge.
The philosophical position that there is only one correct logic or logical system that accurately captures the principles of valid reasoning. [177] logical operator A symbol or function in logic that applies to one or more propositions, producing another proposition that expresses a logical operation such as negation, conjunction, or disjunction.
Deductive reasoning is the process of drawing valid inferences. An inference is valid if its conclusion follows logically from its premises , meaning that it is impossible for the premises to be true and the conclusion to be false.
The validity of an inference depends on the form of the inference. That is, the word "valid" does not refer to the truth of the premises or the conclusion, but rather to the form of the inference. An inference can be valid even if the parts are false, and can be invalid even if some parts are true.