Paired structures in knowledge representation.

•An opposite-based approach to fuzzy modeling is presented as a unifying view to basic knowledge representation.•We claim that paired concepts are the basic building blocks for knowledge representation.•We claim the term paired fuzzy sets is not subject to potential conflict with other related theories.•We claim that neutrality arises from the semantic relationship between those paired concepts.•We show that valuation of paired concepts and neutrality through paired structures can naturally evolve into more complex valuation scales.