XLIII. This is very frequently the case with respect to medicinal observations; and from hence springs that enormous disagreement, with respect to the opinions that are alledged to be founded upon them. One says, that he has experienced the efficacy and salutary fruits, of such a medicine, in such a disease; and another insists, that he has administered the same medicine, in the same disease, and under the same circumstances, and found it to be pernicious. One of the two must be mistaken, and I believe it is not very uncommon for both of them to be so; for it might possibly happen, that the medicine neither did good nor harm, and that the administration of it, was a mere matter of indifference, and the thing itself what we call a chip in porridge. But from what could this difference of sentiment and assertion arise? Why from one of them seeing that his patient, after administering the medicine to him grew better, and from the other perceiving, that his after taking it grew worse; although it might possibly happen, that neither the one grew better, nor the other grew worse in consequence of taking the medicine, but from a very different cause. The diseases of the two patients, from their different constitutions, or internal temperaments, (which is for the most part, a thing impenetrable to physicians) might be in such a state, that the one was disposed to abate, and the other to increase. XLIV. And although the patients may be numerous, with respect to whom this experience is alledged; and admitting that they neither all die, nor all recover, every one according to his pre-occupation, will impute to the remedy, either the happiness of those who did well, or the misfortune of those who perished; and unless they shall resolve, to make a computation of the good or bad success of the practice of those who use that medicine, with that of those who never administer it, and compare them carefully together, this doubt will probably never be cleared up. SECT. XII.