لأن طرفيه وهما المسند إليه والمسند إما حقيقتان لغويتان أو مجازان لغويان
For its two sides—the subject and the predicate—may both be linguistically literal or both linguistically figurative; mixed combinations are also possible.
The subject (المسند إليه) is what receives the judgment, such as “الربيع” (spring). The predicate (المسند) is the action or meaning attributed to it, such as “أنبت” (caused to grow).
Lexical literalness concerns the word's meaning. Rational literalness concerns whether the predicate is attributed to its proper bearer. The two tests must not be confused.