That men who exhibit such talent for observation and such acute and active powers of the understanding as many of these authors exemplify in these very works, should, while writing with so much earnestness against each other, fall into one and the same error, and that an error so palpable, is no flattering exhibition of the state of the art of reasoning among the members of the medical profession. The degree in which the science of mind is neglected in our age and country, may it not be justly added? especially in our profession—that science upon the knowledge of which the conduct of every individual mind is so dependent, is truly deplorable. Medicine is an inductive science, the cultivator of which is peculiarly exposed to the danger of making hasty assumptions and of resting in partial views, yet it is not deemed necessary that he should be at all disciplined in the art of induction, or should be cautioned against any sources of fallacy in the practice of making inferences. All the partial and imperfect views of fever which have now been brought before the eye of the reader, originate in one or other of the following errors, obvious as they all are: either that of assuming as a fact what is merely a conjecture; or that of assigning to the genus what belongs only to the species; or that of characterising the disease by what appertains only to a stage; or that of mistaking the effect for the cause. On careful examination it will appear that one or other of these errors, which are as serious as they are palpable, has vitiated in a greater or less degree every generalization of fever that has hitherto been attempted. Thus the believers in debility derive their notion of the whole disease from the phenomena which occur in the first and the last stages only: in these, it is true, they may find abundant evidence of debility: but then they overlook the intermediate stage in which there are generally the most unequivocal indications of increased sensibility in the nervous and increased action in the vascular systems: in this manner they characterise the disease by what appertains only to certain stages of it. Again, when they contend that debility is not only the essence of fever in general, but is really characteristic of every type of it, they affirm what is indisputable of fevers in particular seasons, in particular climates or in particular constitutions; but beyond this their generalization cannot be extended: in this manner they assign to the genus what belongs only to the species. And when Cullen goes on to affirm that the proximate cause of all the morbid phenomena is a “spasm of the extreme vessels,” he commits the additional and more palpable, but not less common error, of assigning as an undoubted fact, as a real and ascertained occurrence, what is only a conjecture, and for which there is not, and for which he does not even attempt to adduce the shadow of evidence.