196 



INDUCTION. 



had now been added, which it was 

 necessary to combine with the old facts 

 into one general description. But 

 this did not aflfect the correctness of 

 the former expression, considered as 

 a general statement of the only facts 

 which it was intended to represent. 

 And so true is this, that, as is well 

 remarked by M. Comte, these ancient 

 generalisations, even the rudest and 

 most imperfect of them, that of uni- 

 form movement in a circle, are so far 

 from being entirely false, that they 

 are even now habitually employed by 

 astronomers when only a rough ap- 

 proximation to correctness is required. 

 " L'astronomie modeme, en detruisant 

 sans retour les hypotheses primitives, 

 envisag^es comme lois reelles du 

 monde, a soigneusement maintenu 

 leur valeur positive et permanente, la 

 propriety de representor commod^- 

 ment les ph^nomenes quand il s'agit 

 d'une premiere ebauche. Nos res- 

 sources a cet ^gard sont meme bien 

 plus etendues, pr^cisdment h cause que 

 nous ne nous faisonsaucune illusion sur 

 la r^alitd des hypotheses ; ce qui nous 

 permet d'employer sans scrupule, en 

 chaque cas, celle que nous jugeons la 

 plus avantageuse."* 



Dr. Whewell's remark, therefore, is 

 philosophically correct. Successive 

 expressions for the colligation of ob- 

 served facts, or, in other words, suc- 

 cessive descriptions of a phenomenon 

 as a whole, which has been observed 

 only in parts, may, though conflicting, 

 be all correct as far as they go. But 

 it would surely be absurd to assert 

 this of conflicting inductions. 



The scientific study of facts may be 

 undertaken for three different pur- 

 poses : the simple description of the 

 facts ; their explanation ; or their 

 prediction : meaning by prediction, 

 the determination of the conditions 

 under which similar facts may be ex- 

 pected again to occur. To the first of 

 these three operations the name of 

 Induction does not properly belong : 

 to the other two it does. Now Dr. 



* Oour$ de Fhiloiophit Potitive, vol. ii. p. 

 999, 



Whewell's observation is true of the 

 first alone. (Considered as a mere 

 description, the circular theory of the 

 heavenly motions represents perfectly 

 well their general features : and by 

 adding epicycles without limit, those 

 motions, even as now known to us, 

 might be expressed with any degree 

 of accuracy that might be required. 

 The elliptical theory, as a mere de- 

 scription, would have a great advan- 

 tage in point of simplicity, and in the 

 consequent facility of conceiving it 

 and reasoning about it ; but it would 

 not really be more true than the other. 

 Different descriptions, therefore, may 

 be all true : but not, surely, different 

 explanations. The doctrine that the 

 heavenly bodies moved by a virtue 

 inherent in their celestial nature ; the 

 doctrine that they were moved by im- 

 pact, (which led to the h3rpothesi8 of 

 vortices as the only impelling force 

 capable of whirling bodies in circles,) 

 and the Newtonian doctrine that they 

 are moved by the composition of a 

 centripetal with an original projectile 

 force ; all these are explanations col- 

 lected by real induction from supposed 

 parallel cases ; and they were all 

 successively received by philosophers, 

 as scientific truths on the subject of 

 the heavenly bodies. Can it be said 

 of these, as was said of the different 

 descriptions, that they sore all true as 

 far as they go ? Is it not clear that 

 only one can be true in any degree, 

 and the other two must be altogether 

 false ? So much for explanations : 

 let us now compare different predic- 

 tions : the first, that eclipses will occur 

 when one planet or satellite is so 

 situated as to cast its shadow upon 

 another ; the second, that they will 

 occur when some great calamity is 

 impending over mankind. Do these 

 two doctrines only differ in the degree 

 of their truth as expressing real facts 

 with unequal degrees of accuracy ? 

 Assuredly the one is true, and the 

 other absolutely false.* 



* Dr. Whewell, in his reply, contests the 

 distinction here drawn, and maintains, 

 that not oul^ different descriptions, but 



