THE FACTS OF SCIENCE 55 



own, which is essentially an age of scientific inquiry, the 

 prevalence of doubt and criticism ought not to be 

 regarded with despair or as a sign of decadence. It is 

 one of the safeguards of progress ; — la critique est la vie 

 de la science, I must again repeat. One of the most fatal 

 (and not so impossible) features for science would be the 

 institution of a scientific hierarchy which would brand 

 as heretical all doubt as to its conclusions, all criticism 

 of its results. 



S 8. — The Scientific Validity of an Inference 



Much of what we have just said with regard to the 

 scientific validity of conceptions holds with regard to the 

 scientific validity of inferences, for conceptions pass im- 

 perceptibly into inferences. The scope of the present 

 work will only permit us to discuss briefly the limits of 

 legitimate inference and induction. For a fuller discus- 

 sion the reader must be referred to treatises on logic, in 

 particular to the chapters on inference and induction in 

 Stanley Jevons' Principles of Science (chapters iv.-vii., 

 x.-xii., especially). In the first place, the inference which 

 is scientifically valid is that which could be drawn by 

 every logically trained normal mind, if it were in posses- 

 sion of the conceptions upon which the inference has been 

 based. Stress must here be laid on the distinction 

 between " could be drawn " and " actually would be drawn." 

 There are many minds which have clearly defined con- 

 researches on the inheritance by guinea-pigs of diseases acquired by their 

 parents during life. These researches were conducted on a large scale and 

 with great expenditure of time and animal life. (Brown -Sequard kept 

 upwards of five hundred guinea-pigs at once.) Yet we must confess that if 

 these experiments were conducted with every precaution that self-criticism 

 might suggest, the "degrading effect " of inflicting disease and pain on this 

 large amount of animal life would have been more than compensated by 

 the light which the experiments might have cast on the socially important 

 problem of the inheritance of acquired characters. Unfortunately, Brown- 

 Sequard's conceptions and inferences do not appear to many biologists valid, 

 and there lies upon this investigator the onus of proving that (i) all possible 

 precautions for the accuracy of the results were actually taken, and (2), being 

 taken, that the experiments were such as could reasonably have been supposed 

 capable of solving the problems proposed. 



