NATURE AND LA IV. 381 



before the comprehensive power of the Newtonian doctrine ; which 

 soon afterwards obtained its verification in the discovery that the 

 regular movements of the planets in their orbital revolution round 

 the sun, show "perturbations" whose actual amounts are found to 

 be exactly conformable to the results of computations based on the 

 assumption that they, too, attract one another in proportion to 

 their respective masses. A like verification was found in the 

 application of the doctrine of gravitation to the familiar phenomena 

 of the tides ; the rationale of which had remained a mystery until 

 Newton traced not only their diurnal rise and fall, but their 

 monthly and annual variations, to the attractive force exerted 

 by the moon (and in a less degree by the sun) upon the waters of 

 the ocean. 



It will not, I believe, be questioned by any one who has 

 carefully studied Newton's writings, that he himself regarded the 

 doctrine of universal gravitation as an hypothesis^ the value of 

 which entirely depends upon the conformity of every deduction 

 that can be drawn from it by the most rigorous mathematical 

 reasoning, with the facts determined or determinable by observa- 

 tion.* But as all experience since his time has but afforded fresh 

 illustrations of that conformity, — as no perturbation, great or 

 small, has been observed in any of the bodies of the solar system, 

 which has not been " accounted for " (to use the familiar phrase) 

 by its conformity with the general doctrine, — and as the orbital 

 movements of double stars round their common centre of gravity 

 are now found to be in equally exact conformity with it, we feel 

 an assurance of its truth, which nothing, save a complete revolu- 

 tion either in the world of matter or in the world of mind, can 

 ever shake. 



But this brings us no nearer to the idea of "government" by 

 that law. That Newton's law is higher and more general than 

 Kepler's — being, to use the language of J. S. Mill, one of those 

 fewest and simplest assumptions from which, being granted, the whole 

 order of Nature would result — does not give it any " power " to 

 produce or maintain that order. It is simply (again to quote 

 J. S. Mill) one of Xkxo^o. feivest general propositions from which all 

 the uniforniitics which exist in the universe might be deductively 



* See note, p. 379. 



