LAW3 OF NATURE. 191 



a ceitain instantaneous impulse originally impressed upon tliem. After 

 this great discovery, Kepler's three propositions, though still called 

 laws, would hai'dly, by any person accustomed to use language with 

 precision, be temied laws ot' nature : that phrase would be reserved 

 for the simpler laws into which Newton, as the expression is, resolved 

 them. 



According to this language, every well grounded inductive generali- 

 zation is either a law of nature, or a result of laws of nature, capable, 

 if those laws are knowai, of being predicted from them. And the prob- 

 lem of Inductive Logic may be summed up in two questions : How to 

 ascertain the laws of nature ? and. How, after having ascertained them, 

 to follow them into their results 1 On the other hand, we must not 

 suffer ourselves to imagine that this mode of statement amounts to a 

 real analysis, or to anything but a mere verbal transformation of the 

 problem ; for the expi'ession, Laws of Nature, means nothing but the 

 uniformities which exist among natural phenomena (or, in other words, 

 the results of induction), when reduced to their simplest expression. 

 It is, however, something to have advanced so far, as to see that the 

 study of nature is the study of laws, not a law ; of uniformities, in the 

 plural number : that the different natural phenomena have their sepa- 

 rate rules or modes of taking place, which, though much intermixed 

 and entangled with one another, may, to a certain extent, be studied 

 apart : that (to resume our former metaphor) the regularity which 

 exists in nature is a web composed of distinct threads, and only to be 

 understood by tracing each of the threads separately ; for which pur- 

 pose it is often necessary to unravel some portion of the web, and ex- 

 hibit the fibres apart. The rules of experimental inquiry are the con- 

 trivances for um-aveling the web. 



§ 2. In thus attempting to ascertain the general order of nature by 

 ascertaining the particular order of the occuiTence of each one of the 

 phenomena of nature, the most scientific proceeding can be no more- 

 than an improved form of that which was primitively pursued by the 

 human imderstanding, as yet undirected by science. When men first 

 formed the idea of studying phenomena according to a stricter and 

 surer method than that which they had in the first instance spontane- 

 ously adopted, they did not, conformably to the well meant but imprac- 

 ticable precept of Descartes, set out from the supposition that nothing 

 had been already ascertained. Many of the uniformities existing 

 among phenomena are so constant, and so open ta observation, as to 

 force themselves upon men's involuntary recognition. Some facts are 

 so perpetually and familiarly accompanied by certain others, that manr 

 kind learnt, as children now learn, to expect the one where they found 

 the other, long before they knew how to put their expectation into 

 words, by asserting, in a proposition, the existence of a connexion be- 

 tween those phenomena. No science was needed to teach men that 

 food nourishes, that water drowns, or quenches thirst, that the sun 

 gives light and heat, that bodies fall to the ground. The first scien- 

 tific inquirers assumed these and the like as known truths, and set out 

 from them to discover others which were unknown : nor were they 

 wrong in so doing, subject, however, as they afterwards began to see, 

 to an ulterior revision of these spontaneous generalizations themselves, 

 when the progress of knowledge pointed out limits to them, or showed 



