Some Mental Activities Common to All Methods.
There are certain mental activities, which are so absolutely indispensable to science that they are practically always employed in scientific investigations, however much these may vary in other respects. In a wide sense these mental activities might consequently be called methods of science, and they are frequently so called.
But this practice is objectionable, because it leads to cross division and confusion. What is common to all methods should not itself be called a method, for it only encourages the effacing of important differences and when there are many such factors common to all the methods, or most of them, confusion is inevitable. When the mental activities involved are more or less common to the methods, these must be differentiated by reference to other, variable factors such as the different types of data from which the inferences are drawn, and the different types of order sought or discovered in the different kinds, of phenomena investigated the two sets of differences being, of course, intimately connected.
The mental activities referred to are the following Observation including experiment, analysis and synthesis, imagination, supposition and idealisation, inference inductive and deductive, and comparison including analogy. A few words must be said about each of these but no significance should be attached to the order in which they are dealt with.