204 INDUCTION. 



would follow tlie presence of a sufficiently luminous body, whether 

 darkness had preceded or not. 



We may define, therefore, the cause of a phenomenon to be the an- 

 iecedent, or the concurrence of antecedents, upon which it is invariatly 

 and uncondUionally consequent. Or if we adopt the convenient modi- 

 fication of the meaning of the word cause, which confines it to the as- 

 semblage of positive conditions, without the negative, then instead of 

 "unconditionally," we must say, "subject to no other than negative 

 conditions." 



It is evident, that from a limited number of unconditional sequences, 

 there will result a much greater number of conditional ones. Certain 

 causes being given, that is, certain antecedents which are uncondition- 

 ally followed by certain consequents ; the mere coexistence of these 

 causes will give rise to an unlimited number of additional uniformities. 

 If two causes exist together, the effects of both ^vill exist together ; 

 and if many causes coexist, these causes (by what we shall term here- 

 after, the intermixture of their laws) will give rise to new effects, 

 accompanying or succeeding one another in some particular order, 

 which order will be invariable while the causes continue to coexist, but 

 no longer. The motion of the earth in a given orbit round the sun is 

 a series of changes which follow one another as antecedents and con- 

 sequents, and will continue to do so while the sun's attraction, and the 

 force with which the earth tends to advance in a direct line through 

 space, continue to coexist in the same quantities as at present. But 

 vary either of these causes, and the unvarying succession of motions 

 would cease to take place. The series of the earth's motions, there- 

 fore, though a case of sequence invariable within the limits of human 

 experience, is not a case of causation. It is not unconditional. 



To distinguish these conditionally uniform sequences from those 

 which are uniform unconditionally ; to ascertain whether an apparently 

 invariable antecedent of some consequent is really one of its conditions, 

 or whether, in the absence of that antecedent, the effect would equally 

 have followed from some other portion of the circumstances which are 

 present whenever it occurs ; is a principal part of the great problem 

 of Induction ; and is one of those questions, the principles of the solu- 

 tion of which will, it is to be hoped, result from the inquiry we have 

 undertaken. 



§ 6. Does a cause always stand \%ath its effect in the relation of an- 

 tecedent and consequent] Do we not often say of two simultaneous 

 facts that they are cause and effect — as when we say that fire is the 

 cause of warmth, the sun and moisture the cause of vegetation, and the 

 like 1 It is certain that a cause does not necessarily perish because 

 its effect has been produced ; the two, therefore, do very generally 

 coexist ; and there are some appearances, and some common expres- 

 sions, seeming to imply not only that causes may, but that they must, 

 be contemporaneous with their effects. Cessante causd, cessat ct effec- 

 tus, has been a dogma of the schools : the necessity for the continued 

 existence of the cause in order to the continuance of the effect, seems 

 to have been once a general doctrine among philosophers. Mr. Whe- 

 well observes that Kepler's numerous attempts to account for the 

 motion of the heavenly bodies on mechanical principles, were rendered 

 abortive by his always supposing that the force which set those bodiea 



