Perfect syllogism

A perfect syllogism, according to Aristotle, is a syllogism that is self-evidently or obviously true. This self-evidence of a perfect syllogism derives (according to some scholastic writers) directly from the principle of dici de omni, and applies to syllogisms of the first figure. Syllogisms in other figures are also valid by the dici de omni, but are not transparent, because in order to apply dici de omni there must be a process of conversion, or rearrangement of terms, or using the relationships of contrariety and contradiction that are implicit in the square of opposition.