HKB
action and self-direction or automatic character, are in reality the objective and subjective expression of the same factor--namely, the changed relation of man towards the work in which he co-operates.
Some of the directing or mental effort, skill, art, thought, must be taken over, that is to say, some of the processes must be guided not directly by man but by other processes, in order to constitute a machine. A machine thus becomes a complex tool in which some of the processes are relatively fixed, and are not the direct expression of human activity. A machinist who feeds a machine with material may be considered to have some control over the pace and character of the first process, but only indirectly over the later processes, which are regulated by fixed laws of their construction which make them absolutely dependent on the earlier processes. A machine is in the nature of its work largely independent of the individual control of the "tender," because it is in its construction the expression of the individual control and skill of the inventor. A machine, then, may be described as a complex tool with a fixed relation of processes performed by its parts. Even here we cannot profess to have reached a definition which enables us in all cases to nicely discriminate machine from tool. It is easy to admit that a spade is a tool and not a machine, but if a pair of scissors, a lever, or a crane are tools, and are considered as performing single simple processes, and not a number of organically relative processes, we may by a skilfully arranged gradation be led on to include the whole of machinery under tools. This difficulty is of course one which besets all work of definition.
But while it is not easy by attention to complexity of structure always to distinguish a tool from a machine, nothing is gained by making the differentia of a machine to consist in the use of a steam or other non-human motor.