Deductive reasoning and the argument is “valid”, it is possible for the conclusion to be false (determined to be false with a counterexample or other means). Aristotle started documenting deductive reasoning in the 4th century BC. Deductive reasoning Deductive reasoning, also deductive logic, logical deduction is the process of reasoning from one or more statements (premises) to reach a logically certain conclusion. Deductive reasoning goes in the same direction as that of the conditionals, and links premises with conclusions. If all premises are true, the terms are clear, and the rules of deductive logic are followed, then the conclusion reached is necessarily
Logical disjunction is true in that case. An operand of a disjunction is called a disjunct. Related concepts in other fields are: Or is usually expressed with an infix operator: in mathematics and logic, ∨; in electronics, +; and in most programming languages, |, ||, or or. In Jan Łukasiewicz's prefix notation for logic, the operator is A, for Polish "alternatywa" (English: alternative). Logical disjunction is an operation on two logical values, typically the values of two propositions, that has a value of "false" if and only if both of its operands are false. More generally, a disjunction is a logical formula