Tools and Machines

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Tools and machines are almost universally thought of as beneficial, which would make their invention morally praiseworthy. Indeed, without tools it is difficult to see how human beings could survive, and the increasing adoption of machines shows that most people see them as salutary contributions to human affairs. Although isolated tools or particular machines may on occasion be criticized for their negative impacts, this is done mostly to improve technological implements or to reform their uses. Nevertheless, one may note important distinctions between tools and machines as such, and how these distinctions, independent of any particular uses, may be ethically significant.


What is the difference between a tool and a machine? This question is complicated by lexicographic shifts over time. The Greek and Latin words for machine (mechane and machina) name a kind of tool (organum or instrumentum) for lifting heavy weights. Classical mechanics identified six basic types of such machines: the lever, wedge, wheel and axle, pulley, screw, and inclined plane. Machines, unlike other tools, presented a conundrum: How do they enable human users to lift weights that would otherwise be beyond their power to move?

Unlike with a stick used for poking or scratching, which serves as a straightforward extension of some human operation, determining how machines work is more difficult. Aristotle's Mechanical Problems was an early attempt to solve the mystery concerning how machines do what they do, that is, how they work or operate. What happens is that all six simple machines function as machines by transforming a smaller force exerted over a longer distance into a greater force exerted over a shorter distance by means of a structured redirection of the force in question.

But machines in this premodern sense are just one kind of tool. All tools, even simple machines, require two types of direct human inputs: energy and guidance. The hammer is swung with the arm and guided by hand–eye coordination. By contrast, machines in a modern sense require only one type of direct human input: guidance. The difference is that between a human-powered and -guided bicycle and a human-guided car; a person does not pedal a car, but simply drives it.

After human beings have constructed them or found natural objects with properties such that they can be used as tools, any use will involve some energy and guidance from a user. The guidance, precisely because it constitutes the introduction of intelligence, involves skill. In this sense the skillful use of tools is different from the more passive use of other artifacts such as baskets, chairs, and houses. The coordination of human power inputs, as when a group of men operates a battering ram, and the substitution of animal and other non-human sources of power such as wind for human power, foreshadow the development of machines in the modern sense.

The standard definition for the modern machine is: "a combination of resistant bodies so arranged that by their means the mechanical forces of nature can be compelled to do work accompanied by certain determinate motions." Alternatively, a machine is an "assemblage of resistant bodies, connected by movable joints, to form a closed kinematic chain with one link fixed and having the purpose of transforming motion." (Both definitions are from Franz Reuleaux, who in the late 1800s formulated the modern science of mechanics.) Mechanics, or the science of machines, analyzes the ways forces are compelled and transformed to do work in terms of their structures (statics) and functional operations (dynamics).

Functions and Uses

Tools and machines have internal operations or workings that can be used for many different purposes. These operations are commonly analyzed in modular terms: Gears slow down or speed up motion. A cam transforms reciprocal into rotary motion. Although how tools and machines operate or function does not fully determine their uses, they place boundary conditions on or for possible uses. Indeed, when an inventor applies for a patent on a new machine, the inventor is required to specify both its (external) use and how (internally) it is designed to operate or function so as to make possible the intended use. Engineering design thus considers both extrinsic use and internal structure and operation, and is successful when it unites the two.

But just as with the tool–machine distinction, so that between function and use is difficult to nail down. In many instances the word function can be replaced by the words working, operation, or even use. One must be careful in speaking about functions not to create an imaginary ontological substance that is nothing more than projected use. But to say that the machine operations or functions of pounding, drilling, or rotating are the uses of pounding, drilling, or rotating shifts attention from the structure of the machine and how it works to the intentions or purposes of the user.

For engineers who focus on machines, then, machines and their component parts are as often distinguished by operations or functions as by uses. Indeed, it is precisely in this sense that classical machines are distinguished from tools. The machine works to increase force across decreasing distance in ways that other tools do not. Moreover, the working or functioning of tools as tools depends on human energy and skillful guidance; modern machines work or function with only human guidance. Because of this, using machines requires less human work and, by placing greater and greater power in human hands, makes consciousness or forethought an ethical imperative. One does not have to be nearly as conscious about what is going on when riding a bicycle as when driving an automobile.

In general the experience of using machines is different from that of using tools in terms of the decline in human energy input and a corresponding increase in human mental input. This transformation of the use experience is of ethical significance and is independent of any particular use. It is true no matter what kind of machine one is operating and what one is producing with it or where one might be traveling in it. No matter what kind of machines are involved, machine users are morally obligated to think more than tool users about what is going on. To some extent this shift in the character of the use experience may also be described as setting the pattern for living in a machine-dominated technological world.


SEE ALSO Animal Tools.


Mitcham, Carl. (1994). Thinking through Technology: The Path between Engineering and Philosophy. Chicago: University of Chicago Press. See especially chapter 7, "Types of Technology as Object."

Reuleaux, Franz. (1876). The Kinematics of Machinery: Outlines of a Theory of Machines, trans. and ed. Alex B. W. Kennedy. London: Macmillan. Translation of Theoretische Kinematik: Grundzüge einer Theorie des Maschinenwesens, 1875.