As mentioned before, the most effective solutions are achieved when an inventor solves a technical problem that contains a contradiction. When and where does a contradiction occur? It occurs when we are trying to improve one characteristic, or parameter, of a technical system and cause another characteristic, or parameter, of the system to deteriorate. A compromise solution is then usually considered. A technical system has several characteristics (parameters) — weight, size, color, speed, rigidity, and so on. These characteristics describe the physical state of a technical system. When solving technical problems, these
characteristics help determine the technical contradiction residing in the system.
Increasing the power of an engine (positive improvement) requires an increase in the size of the engine (negative effect). So, an inventor considers increasing the power partially in order to reduce the negative effect (compromise solution). To increase the speed of an airplane, a new and more powerful engine is installed. This increases the weight of the airplane so the wings can no longer support it during takeoff. Increasing the wing size produces more drag, slowing the airplane down. These are some examples of how improvements can produce contradictions. The improvement goals were never fully achieved because the root technical contradictions were never resolved. These are called technical contradictions because they happen inside of technical systems. The 40 Principles are used to resolve technical contradictions.
There is another type of contradiction — physical contradiction — appearing when two opposite properties are required from the same element of a technical system or from the technical system itself. There are different methods for resolving physical contradictions (separation of contradictory requirements in time or space, changing the physical state of a substance, separation upon condition).
1. Landing gear must be present on an airplane in order to land and takeoff. It should not be present during flight because of an increase in air drag. The physical contradiction is that the landing gear must be both present and absent. This contradiction is resolved by separating the requirements in time — make the landing gear retractable.
2. For high water diving, water must be “hard” to support the diver and “soft” so as not to injure the diver. The physical contradiction: The water must be hard and soft at the same time. This contradiction is resolved by separating the requirements in space: Saturate the water with air bubbles — the pool contains both air and water.