OBSERVATION AND EXPERIMENT. 423 



the evidence of experiment to that of simple observation. 

 Until we had done so, we had only proved invariable ante 

 cedence within the limits of experience, but not unconditional 

 antecedence, or causation. Until it had been shown by the 

 actual production of the antecedent under known circum 

 stances, and the occurrence thereupon of the consequent, that 

 the antecedent was really the condition on which it depended ; 

 the uniformity of succession which was proved to exist between 

 them might, for aught we knew, be (like the succession of day 

 and night) not a case of causation at all ; both antecedent and 

 consequent might be successive stages of the effect of an ulte 

 rior cause. Observation, in short, without experiment (sup 

 posing no aid from deduction) can ascertain sequences and 

 coexistences, but cannot prove causation. 



In order to see these remarks verified by the actual state 

 of the sciences, we have only to think of the condition of 

 natural history. In zoology, for example, there is an immense 

 number of uniformities ascertained, some of coexistence, others 

 of succession, to many of which, notwithstanding considerable 

 variations of the attendant circumstances, we know not any 

 exception : but the antecedents, for the most part, are such as 

 we cannot artificially produce ; or if we can, it is only by set 

 ting in motion the exact process by which nature produces 

 them; and this being to us a mysterious process, of which 

 the main circumstances are not only unknown but unobserv- 

 able, we do not succeed in obtaining the antecedents under 

 known circumstances. What is the result ? That on this 

 vast subject, which affords so much and such varied scope for 

 observation, we have made most scanty progress in ascertaining 

 any laws of causation. We know not with certainty, in the 

 case of most of the phenomena that we find conjoined, which 

 is the condition of the other ; which is cause, and which effect, 

 or whether either of them is so, or they are not rather conjunct 

 effects of causes yet to be discovered, complex results of laws 

 hitherto unknown. 



Although some of the foregoing observations may be, in 

 technical strictness of arrangement, premature in this place, it 

 seemed that a few general remarks on the difference between 



