Take an instance. In making an inquiry into the causes of fatigue, Professor Mosso of Turin selected two dogs as nearly alike as possible. One he kept tied, and the other he exercised until it was thoroughly tired. He then transfused blood of the tired dog into the veins of the rested one, and produced in the latter every sign of fatigue. From this he concluded that fatigue was due to certain poisons in the blood. Now we cannot contradict the fact of this experiment: that the rested animal was made to look tired. But we can question the inference drawn. The truth of the conclusion aside, was the evidence sufficient to establish it? Might not, for instance, similar results have been produced upon the rested dog if blood of another rested dog had been transfused into it? Had Mosso made such an experiment? Other objections should easily occur to one. Questions which admit of treatment by studying both sides are too numerous to mention. The literature of philosophy furnishes particularly good material. Examples which at present occur to me are Sir William Hamilton’s philosophy versus Mill’s _Examination of Sir William Hamilton’s Philosophy_, and Herbert Spencer’s _First Principles_ versus William James’ essay, _Herbert Spencer’s Autobiography_ and Henri Bergson’s criticism of Spencer in his _Creative Evolution_. Uncritical students of the history of philosophy often find themselves agreeing with each thinker in turn, no matter how much he contradicts previous thinkers, and end by acquiescing in the last system they read about. I remember a philosophy class which completed its studies with Pragmatism. Of course it was merely a coincidence, but at the end of the course fully nine-tenths of the students declared themselves Pragmatists! It is almost needless to remark that an author who pretends to point out fallacies in another is not necessarily right. There are men who pride themselves on “reading both sides of a subject”; but unless they have been critical, their knowledge is not half as clear or as likely to be true as that of a man who has read only one side, but who has read it critically. * * * * * We have now to consider the next step outlined in the suggested plan of reading—“written note should be made of the problems taken up which you do not believe have been adequately treated, or the solutions of which are in any way unsatisfactory. These you should think out for yourself.”