Analysis of information sources in references of the Wikipedia article "Categorical proposition" in English language version.
In the process of obversion, we change the quality of a proposition (from affirmative to negative or from negative to affirmative), and then replace its predicate with the negation or complement of the predicate.
In the process of obversion, we change the quality of a proposition (from affirmative to negative or from negative to affirmative), and then replace its predicate with the negation or complement of the predicate.
A categorical statement is an assertion or a denial that all or some members of the subject class are included in the predicate class.
During the Middle Ages, logicians gave the four categorical forms the special names of A, E, I, and O. These four letters came from the first two vowels in the Latin word 'affirmo' ('I affirm') and the vowels in the Latin 'nego' ('I deny').
