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Simple conversion العَكْسُ المُسْتَوِي

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Simple conversion

al-ʿaks al-mustawī

العَكْسُ المُسْتَوِي

(ʿaks mustawī) makes the of a its and the predicate its subject, keeping its quality and its truth.

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In a picture

“Every human is an animal” converts to “Some animal is human”, not to “Every animal is human”: part of “animal” lies outside “human”.

Explanation

A to a universal negative, and a to a particular affirmative.

A only to a , and a has no converse.

Also written as: aks, aks mustawi, conversion.

In the text

الْعَكْسُ هُوَ: أَنْ يُصَيَّرَ الْمَوْضُوعُ مَحْمُولًا، وَالْمَحْمُولُ مَوْضُوعًا، مَعَ بَقَاءِ السَّلْبِ وَالإِيجَابِ بِحَالِهِ، وَالتَّصْدِيقِ وَالتَّكْذِيبِ بِحَالِهِ.Conversion is making the subject the predicate and the predicate the subject, while negation or affirmation stays as it was, and truth or falsity stays as it was.وَالْمُوجَبَةُ الْكُلِّيَّةُ لَا تَنْعَكِسُ كُلِّيَّةً، إِذْ يَصْدُقُ قَوْلُنَا: كُلُّ إِنْسَانٍ حَيَوَانٌ، وَلَا يَصْدُقُ: كُلُّ حَيَوَانٍ إِنْسَانٌ، بَلْ تَنْعَكِسُ جُزْئِيَّةً، لِأَنَّا إِذَا قُلْنَا: كُلُّ إِنْسَانٍ حَيَوَانٌ، يَصْدُقُ: بَعْضُ الْحَيَوَانِ إِنْسَانٌ، فَإِنَّا نَجِدُ الْمَوْضُوعَ شَيْئًا مَوْصُوفًا بِالإِنْسَانِ وَالْحَيَوَانِ، فَيَكُونُ: بَعْضُ الْحَيَوَانِ إِنْسَانًا.The universal affirmative does not convert as a universal: “Every human is an animal” is true, but “Every animal is human” is not. It converts as a particular: when we say “Every human is an animal”, “Some animal is human” is true, for we find the subject to be something described as both human and animal, so some animal is human.وَالْمُوجَبَةُ الْجُزْئِيَّةُ أَيْضًا تَنْعَكِسُ جُزْئِيَّةً بِهَذِهِ الْحُجَّةِ، وَالسَّالِبَةُ الْكُلِّيَّةُ تَنْعَكِسُ سَالِبَةً كُلِّيَّةً، وَذَلِكَ بَيِّنٌ بِنَفْسِهِ، فَإِنَّهُ إِذَا صَدَقَ: لَا شَيْءَ مِنَ الإِنْسَانِ بِحَجَرٍ، صَدَقَ: لَا شَيْءَ مِنَ الْحَجَرِ بِإِنْسَانٍ.The particular affirmative likewise converts as a particular, by the same argument. The universal negative converts as a universal negative, and that is evident by itself: if “No human is a stone” is true, then “No stone is human” is true.وَالسَّالِبَةُ الْجُزْئِيَّةُ لَا عَكْسَ لَهَا لُزُومًا، فَإِنَّهُ يَصْدُقُ: بَعْضُ الْحَيَوَانِ لَيْسَ بِإِنْسَانٍ، وَلَا يَصْدُقُ عَكْسُهُ.The particular negative has no converse that necessarily follows: “Some animal is not human” is true, but its converse is not.وَالثَّانِي يَرْتَدُّ إِلَى الأَوَّلِ بِعَكْسِ الْكُبْرَى، وَالثَّالِثُ يَرْتَدُّ إِلَيْهِ بِعَكْسِ الصُّغْرَى، وَالرَّابِعُ يَرْتَدُّ إِلَيْهِ بِعَكْسِ التَّرْتِيبِ أَوْ بِعَكْسِ الْمُقَدِّمَتَيْنِ جَمِيعًا.The second figure is brought back to the first by converting the major premise, the third by converting the minor, and the fourth by reversing the order of the premises or by converting both.

Examples

“Every human is an animal” converts to “Some animal is human”

Related terms

Practise

4 question(s) on this term, in the practice set for propositions.

Go to practice · 8 questions

Test yourself

3 questions. With 6 out of 10 or more (two stars) the next term opens.

Question 1
What does simple conversion (ʿaks mustawī) do to a proposition?
Question 2
What is the simple converse of “Every writer is a human”?
Question 3
“Not every animal is a human” is true, but “Not every human is an animal” is false. What does this show?

Next: Syllogism القِيَاس