390 INDUCTION. 



years past, but they do not include the future. Yet we infer with confi- 

 dence that the sun will rise to-morrow; and nobody doubts that we are 

 entitled to do so. Let us consider what is the warrant for this confidence. 



In the example in question, we know the causes on which the derivative 

 uniformity depends. They are : the sun giving out light, the earth in a 

 state of rotation and intercepting light. The induction which shows these 

 to be the real causes, and not merely prior effects of a common cause, be- 

 ing complete, the only circumstances which could defeat the derivative law 

 are such as would destroy or counteract one or other of the combined 

 causes. While the causes exist and are not counteracted, the effect will 

 continue. If they exist aqd are not counteracted to-morrow, the sun will 

 rise to-morrow. 



Since the causes, namely, the sun and the earth, the one in the state of 

 giving out light, the other in a state of rotation, will exist until something 

 destroys them, all depends on the probabilities of their destruction, or of 

 their counteraction. We know by observation (omitting the inferential 

 proofs of an existence for thousands of ages anterior) that these phenomena 

 have continued for (say) five thousand years. Within that time there has 

 existed no cause sufticient to diminish them appreciably, nor which has 

 counteracted their effect in any appreciable degree. The chance, therefore, 

 that the sun may not rise to-morrow amounts to the chance that some 

 cause, which has not manifested itself in the smallest degree during five 

 thousand years, will exist to-morrow in such intensity as to destroy the 

 sun or the earth, the sun's light or the earth's rotation, or to produce an 

 immense disturbance in the effect resulting from those causes. 



Now, if such a cause will exist to-morrow, or at any future time, some 

 cause,proximate or remote, of that cause must exist now, and must have ex- 

 isted during the whole of the five thousand years. If, therefore, the sun do 

 not rise to-morrow, it will be because some cause has existed, the effects of 

 which, though during five thousand years they have not amounted to a per- 

 ceptible quantity, will in one day become overwhelming. Since this cause 

 has not been recognized during such an interval of time by observers sta- 

 tioned on our earth, it must, if it be a single agent, be either one whose 

 effects develop themselves gradually and very slowly, or one which existed 

 in regions beyond our observation, and is now on the point of arriving in 

 our part of the universe. Now all causes which we have experience of act 

 according to laws incompatible with the supposition that their effects, af- 

 ter accumulating so slowly as to be imperceptible for five thousand years, 

 should start into immensity in a single day. No mathematical law of pro- 

 portion between an effect and the quantity or relations of its cause could 

 produce such contradictory results. The sudden development of an effect 

 of which there was no previous trace always arises from the coming to- 

 gether of several distinct causes, not previously conjoined ; but if such sud- 

 den conjunction is destined to take place, the causes, or ^/i6^V causes, must 

 have existed during the entire five thousand years ; and their not having 

 once come together during that period shows how rare that particular com- 

 bination is. We have, therefore, the warrant of a rigid induction for con- 

 sidering it probable, in a degree undistinguishable from certainty, that the 

 known conditions requisite for the sun's rising will exist to-morrow. 



§ 3. But this extension of derivative laws, not causative, beyond the lim- 

 its of observation can only be to adjacent cases. If, instead of to-morrow, 

 we had said this day twenty thousand years, the inductions would have 



