In first order logic, reasoning can be done from two points of view: either using syntax alone, or including semantic terms. First order logic is different from propositional logic: In first order logic, there are "quantifiers", called "for all" (written as formula_1) and "there is at least one" (written as formula_2). Negation, conjunction, inclusive disjunction, exclusive disjunction and implication are all defined the same way as in propositional logic. Because of that, first order logic can be thought of as an extension of propositional logic. 