The responses to these questions have been innumerable, and nearly all of them raise further difficulties. Some theorists have denied that what one sees in such a case is an existent entity at all but have found it difficult to explain why one seems to see such an entity. Still others have suggested that the image seen in such a case is in one's mind and not really in space. But then what is it for something to be in one's mind, where in the mind is it, and why, if it is in the mind, does it appear to be "out there," in space where the stick is? And above all, how does one decide these questions? The various questions posed above only suggest the vast network of difficulties, and in order to straighten out its tangles it becomes indispensable to develop theories.
In accordance with a proposal made above, epistemology, or thelogic of scientific discovery, -should be identified with the theory of scientific method. The theory of method, in so far as it goes beyond the purely logical analysis of the relations between scientific statements, is concerned with the choice of methods—with decisions about the way in which scientific statements are to be dealt with. These decisions will of course depend in their turn upon the aim, which we choose from among a number of possible aims.
Methodology or ascientificmethod is a collective term denoting the various processes by the aid of which the sciences are built up. In a wide sense, any mode of investigation by which scientific or other impartial and systematic knowledge is acquired is called a scientific method.
What are the rules of scientific method, and why do we need them? Can there be a theory of such rules, a methodology? The way in which one answers these questions will largely depend upon one's attitude to science. The way in which one answers these questions will largely depend upon one's attitude to science. Those who, like the positivists, see empirical science as a system of statements, which satisfy certain logical criteria, such as meaningfulness or verifiability, will give one-answer. A very different answer will be given by those who tend to see the distinguishing characteristic of empirical statements in their susceptibility to revision—in the fact that they can be criticised,-and superseded by better ones; and who regard it as their task to analyse the characteristic ability of science to advance, and the characteristic manner in which a choice is made, in crucial cases, between conflicting systems of theories.
Such methods, as it was mentioned above, are of two principal types— technical and logical. A technical or technological method is a method of manipulating the phenomena under investigation, measuring them with precision, and determining the conditions under which they occur, so as to be able to observe them in a favourable and fruitful manner. A logical method is a method of reasoning about the phenomena investigated, a method of drawing inferences from the conditions under which they occur, so as to interpret them as accurately as possible. The term "scientific method" in the first instance probably suggests to most minds the technical methods of manipulation and measurement. These technical methods are very numerous and they are different in the different sciences. Few men ever master the technical methods of more than one science or one group of closely connected sciences. An account of the most important technical methods is usually given in connection with the several sciences. It would be impossible, even if it were desirable, to give a useful survey of all, or even of the most important, technical methods of science. It is different with the logical methods of science. These methods of reasoning from the available evidence are not really numerous, and are essentially the same in all the sciences. It is both possible and desirable to survey them in outline. Moreover, these logical methods of science are in a very real sense the soul of the technical methods.
In pure science the technical methods are not regarded as an end in themselves, but merely as a means to the discovery of the nature of the phenomena under investigation. This is done by drawing conclusions from the observations and experiments, which the technical methods render possible. Sometimes the technical methods make it possible for the expert investigator to observe and measure certain phenomena, which otherwise could either not be observed and measured at all, or not so accurately. Sometimes they enable him so to determine the conditions of their occurrence that he can draw reliable conclusions about them, instead of having to be content with unverified conjectures. The highly speculative, mainly conjectural character of early science was no doubt due entirely to the lack of suitable technical methods and scientific instruments. In a sense; therefore, it may be said that the technical methods of science are auxiliary to the logical methods, or methods of reasoning. And it is these methods that are to be considered in the present article. The technical methods of science, as ought to be clear from the preceding remarks, are of first rate importance, 'and we have not the remotest desire to underrate them; but it would be futile to attempt to survey them here.
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.
Observation and Experiment.
Observation is the act of apprehending things and events, their attributes and their concrete relationships. From the point of view of scientific interest two types of observation may be distinguished, namely: (1) The bare observation of phenomena under conditions which are beyond the control of the investigator, and (2) experiment, that is, the observation of phenomena under conditions controlled by the investigator. What distinguishes experiment from bare observation is control over what is observed, not the use of scientific apparatus, nor the amount of trouble taken. The mere use of telescopes or microscopes, etc., even the selection of specially suitable times and places of observation, does not constitute an experiment, if there is no control over the phenomenon observed. On the other hand, where there is such control, there is experiment, even if next to no apparatus be used, and the amount of trouble involved be negligible. The making of experiments usually demands the employment of technical methods, but the main interest centres in the observations made possible thereby. The great advantage of experiment over bare observation is that it renders possible a more reliable analysis of complex phenomena, and more reliable inferences about their connections, by the variation of circumstances, which it effects. Its importance is so great that people commonly speak of "experimental method." The objection to this is that experiment may be, and is, used in connection with various methods, which are differentiated on other, and more legitimate, grounds. To speak of a method of observation is even less permissible, seeing that no method can be employed without it.
Analysis and Synthesis.
The phenomena of nature are very complex and, to all appearances, very confused. The discovery of any kind of order in them is only rendered possible by processes of analysis and synthesis. These are as essential to all scientific investigation as is observation itself. The process of analysis is helped by the comparison of two or more objects or events that are similar in some respects and different in others. But while comparison is a necessary instrument of analysis, analysis, in its turn, renders possible more exact comparison. After analysing some complex whole into its parts or aspects, we may tentatively connect one of these with another in order to discover a law of connection, or we may, in imagination, combine again some of them and so form an idea of what may be common to many objects or events, or to whole classes of them. Some combinations so obtained may not correspond to anything that has ever been observed. In this way analysis and synthesis, even though they are merely mental in the first instance, prepare the way for experiment, for discovery and invention.