Dorst's equation: WHAT + HOW = VALUE and three modes of reasoning
In design, we reason differently from classical deduction. Kees Dorst describes the core equation as WHAT + HOW = VALUE, where WHAT is the thing being designed, HOW is the working principle or frame, and VALUE is the desired outcome. In deduction we know WHAT and HOW and derive VALUE. In normal abduction we know HOW and VALUE and must design the WHAT. In design abduction — the most challenging mode — only VALUE is known, and we must create both WHAT and HOW from scratch.