Behaviour boundary theory

Classical supply and demand models assume that price and quantity operate freely within the mathematically defined positive quadrant. However, real markets demonstrate robust non-negative constraints that arise not only from mathematics but also from human behaviour. This paper introduces the concept of a Behavioural Boundary: an invisible but binding condition that prevents price, quantity, and profit from entering negative regions. This boundary emerges because producers avoid negative profits, consumers avoid negative utility, and both sides require minimum regular supply. We formalize this idea using the absolute value function and explore its implications for market behaviour and equilibrium.