Volume 1
A course of lectures on natural philosophy and the mechanical arts / by Thomas Young.
- Thomas Young
- Date:
- 1845
Licence: Public Domain Mark
Credit: A course of lectures on natural philosophy and the mechanical arts / by Thomas Young. Source: Wellcome Collection.
Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.
46/670 page 12
![In tlie application of induction the greatest caution and circumspection are necessary; for it is obvious that, before we can infer with certainty the complete similarity of two events, we must be perfectly weU assured that we are acquainted with every circumstance which can have any rela- tion to their causes. The error of some of the ancient schools consisted principally in the want of sufficient precaution in this respect; foralthougli Bacon is, with great justice, considered as the author of the most correct method of induction, yet, according to his own statement, it was chiefly the guarded and gradual application of the mode of argument that he laboured to introduce. He remarks that the Aristotelians, from a hasty observa- tion of a few concurring facts, proceeded immediately to deduce universal principles of science and fundamental laws of nature, and then derived from these, by their syllogisms, all the parficular cases which ought to have been made intennediate steps in the inquiry. Of such an error we may easily find a familiar instance. We observe that, in general, heavy bodies fall to the ground unless they are supporfed ; it was therefore con- cluded that aU heavy bodies tend downwards ; and since flame was most frequently seen to rise upwards, it was inferred that flame was naturally and absolutely light. Had sufficient precaution been employed in observ- ing the effects of fluids on falling and on floating bodies, in examining the relations of flame to the circumambient atmosjohere, and in ascertaining the sjjecific gravity of the air at different temperatures, it would readily have been discovered that the greater weight of the colder air was the cause of the ascent of the flame,—flame being less heavy than air, but yet having no positive tendency to ascend. And, accordingly, the Epicureans, Avhose arguments, as far as they related to matter and motion, were often more accurate than those of their cotemporaries, had corrected this error ; for we find in the second book of Lucretius a very just explanation of the ])henomenon. “ See with what force yon river’s crystal stream Resists the weight of many a massy beam. To sink the wood the more we vainly toil, The higher it rebounds, with swift recoil. Yet that the beam would of itself ascend No man will rashly venture to contend. Thus too the flame has weight, though higlily rare. Nor mounts but when compelled by heavier air.” It may be proper to notice here those axioms which are denominated by Newton • rules of philosophizing; although it must be confessed that they render us very little immediate assistance in our investigations. The first is, that “ no more causes are to be admitted as existing in nature than are true and sufficient for explaining the phenomena to be considered tlie second, “ therefore effects of the same kind are to be attributed, as far as is possible, to tlie same causesthirdly, “ those qualities of bodies which cannot be increased nor diminished, and which are found in all bodies v/ithin the reach of our experiments, are to be considered as general * Principia ; Introduction to Book III.](https://iiif.wellcomecollection.org/image/b21301840_0001_0046.jp2/full/800%2C/0/default.jpg)
