I The Method of Argument

or wrong. The history of science shows that concepts have gone on changing, sometimes because greater minds have applied themselves to them, and sometimes because the field of scientific discovery has been widened by the increasing sophistication and rapid evolution of modern technology. Therefore, holding any given method of reasoning valid does not mean necessarily that the particular method must surely be right. And the possibility must always be kept in mind that the conclusions arrived at may be wrong. The validity of both criteria and conclusions are inevitably open to the challenge of subsequent discoveries. Of the fourth method of reasoning, it can be said that there is no direct link between hypothesis and observation; it is solely inference which provides the necessary connection. Then why should it be taken for granted that our inference is necessarily correct? In making inferences it is quite possible to err, but this probability of error should not affect the validity of the criterion in question. If it is possible to doubt the validity of the criterion because of a perceived error in inference, then on the same grounds, other criteria will also be exposed to doubt. Consider that it is on this that the whole edifice of our modern science rests. There is no question of all established scientific concepts having been the result of or having been confirmed by observation and experiment. Certain theories have been developed on the basis of a purely external approach. Here what links theory and observation is actually inference. When a scientist says, ‘Electricity means a flow of electrons,’ he does not mean that he has seen electrons flowing along an electric wire by means of a microscope. All he is actually doing is explaining an observed chain of events, which entails turning on the switch that makes the bulbs light up, the fans rotate, and the factories start functioning. Thus, what has come within his experience is simply an external phenomenon and is not by any means the inferred event. In this respect, all scientific concepts are inferences arrived at by applying the fourth method of reasoning. The only difference, it would appear, between the third and fourth criteria, or methods of reasoning, is that according to the