«العكس المستوي، ويقال له: العكس المستقيم أيضاً، وهو عبارة عن جعل الجزء الأول من القضية ثانياً، والجزء الثاني أولاً مع بقاء الصدق والكيف»
Simple conversion, also called direct conversion, places the first part of a proposition second and the second first, while preserving truth and quality.
In a categorical proposition, interchanging the parts means exchanging subject and predicate. Preserving truth means that a true original must yield a true converse. Preserving quality means affirmatives remain affirmative and negatives remain negative.
Preserving quantity is not required: a universal proposition may validly convert into a particular one.