A proposition is a statement affirming a positive or negative relation between two concepts. Propositions are therefore either true or false. Such that if a statement can be neither true nor false, then this statement is not a proposition.
For example: “God exists” is a proposition relating existence to God.
Propositions are composed of three parts: the subject (Al-Mawdu’), the predicate (Al-Mahmul), and the relation (Al-Nisba).
Subject: that which the predicate is related to.
Predicate: that which is related to the subject.
Relation: the positive or negative relationship between the subject and predicate.
For example: if we break the proposition “God exists” into the three parts outlined above, we get:
God as the subject, existence as the predicate, and the relating of existence to God as a positive relation .
The Law of Non-Contradiction
The law of non-contradiction (Qanun Imtina’ Al-Tanaqud) dictates that a proposition and its negation are mutually exclusive and collectively exhaustive. This is because the essence of a proposition’s truth, is its being not-false. And the essence of a proposition’s being false, is its non-truth.
Thus, if a proposition is true, then its negation is false. And if a proposition is false, then its negation is true.
For example: since the proposition “even numbers are divisible by two” is true, its negation (“even numbers are not divisible by two”) is false by law of non-contradiction.
 Postive relation because this proposition affirms existence to God.
Inversely, the proposition “God does not exist” is a proposition negating existence from God. It is therefore a proposition consisting of a negative relation between the subject and the predicate.
 The negation of a given proposition, is another statement identical to it in all respects, except that its relation is inverted. In other words, the relation of the negation is positive if the original proposition’s relation is negative, and negative if the original’s relation is positive. Negations can often be expressed by simply prefixing the predicate of the original proposition with a “not”.
For example: the negation of the proposition “even numbers are divisible by two” is “even numbers are not divisible by two”.
 “Mutually Exclusive” meaning: both propositions cannot be true.
 “Collectively Exhaustive” meaning: both propositions cannot be false.