How machine is engineered?

A machine is defined as an apparatus for applying mechanical power, consisting of a number of interrelated parts, each having a definite function. The manufacture of a machine consists of cutting suitably shaped parts and fitting them together so that their joint mechanical action should provide a required function. The structure of machines and the working of their structure are thus shaped by man, even while their material and the forces that operate them obey the laws of inanimate nature. In constructing a machine and supplying it with power, we harness the laws of nature at work in the machine’s material and its driving force, and make them serve our purpose. This harness is not unbreakable; the structure of the machine, and thus its working, can break down. But this will not affect the forces of inanimate nature on which the operation of the machine relied; it merely releases these forces from the restriction the machine imposed on them before it broke down.

Therefore the machine, as a whole, works under control of two distinct principles: the higher principle, the machine’s design and the lower principle, the law of inanimate nature on which the machine relies. Higher level properties are emergent in the sense that they are not reducible to the lower level principles. (For example, the shape of a cup is not reducible to the laws of physics.) The higher level harnesses the lower one, the lower level is the foundation and therefore independent of the level above. Hence, a machine is a system of dual control that relies, for the operations of its higher principle, on the working of the lower principle.

The higher-level relies for its operations on the level below and reduces the scope of the operation of the particulars at the level below by imposing on it a boundary that harnesses it to the service of the higher level. Because any machine operates under two levels of constraints, the design of machine therefore is to first identify the particulars of the lower level and its governing constraint and then synthesize the higher-level constraint, or ways of harnessing lower level particulars, to implement required functions.

The main task of engineers is to apply their scientific knowledge, the knowledge of lower-level principles to identify lower level particulars and their governing laws, and technological knowledge, the knowledge of higher-level principles or the knowledge of design to implement required functions, to the solution of technical problems. They then optimize these solutions within the requirements and constraints of the project. For example, electronic engineers apply circuit design knowledge to the electronic properties of materials to build circuits. Mechanical engineers apply mechanical design knowledge to the mechanical properties of different materials to build machines. Without a solid knowledge of the material mechanics, the lower level principle, we build bridges that cannot be accounted for.