HUMAN NATURE A SUBJECT OF SCIENCE. 58V 



ficulty inherent in the peculiar nature of those phenomena), the science is 

 extremely imperfect ; and were it perfect, might probably be of little avail 

 in practice, since the data requisite for applying its principles to particular 

 instances would rarely be procurable. 



A case may be conceived, of an intermediate character, between the per- 

 fection of science and this its extreme imperfection. It may happen that 

 the greater causes, those on which the principal part of the phenomena 

 depends, are within the reach of observation and measurement ; so that if 

 no other causes intervened, a complete explanation could be given not only 

 of the phenomena in general, but of all the variations and modifications 

 which it admits of. But inasmuch as other, perhaps many other causes, 

 separately insignificant in their effects, co-operate or conflict in many or in 

 all cases with those greater causes, the effect, accordingly, presents more 

 or less of aberration from what would be produced by the greater causes 

 alone. Now if these minor causes are not so constantly accessible, or not 

 accessible at all, to accurate observation, the principal mass of the effect 

 may still, as before, be accounted for, and even predicted ; but there will 

 be variations and modifications which we shall not be competent to explain 

 thoroughly, and our predictions will not be fulfilled accurately, but only ap- 

 proximately. 



It is thus, for example, with the theory of the tides. No one doubts 

 that Tidology (as Dr. Whewell proposes to call it) is really a science. As 

 much of the phenomena as depends on the attraction of the sun and moon 

 is completely understood, and may, in any, even unknown, part of the 

 earth's surface, be foretold with certainty ; and the far greater part of the 

 phenomena depends on those causes. But circumstances of a local or cas- 

 ual nature, such as the configuration of the bottom of the ocean, the degree 

 of confinement from sliores, the direction of the wind, etc., influence, in 

 many or in all places, the height and time of the tide ; and a portion of 

 these circumstances being either not accurately knowable, not precisely 

 measurable, or not capable of being certainly foreseen, the tide in known 

 places commonly varies from the calculated result of general principles 

 by some difference that we can not explain, and in unknown ones may 

 vary from it by a difference that we ai'e not able to foresee or conjecture. 

 Nevertheless, not only is it certain that these variations depend on causes, 

 and follow their causes by laws of uneri-ing uniformity ; not only, there- 

 fore, is tidology a science, like meteorology, but it is, what hitherto at 

 least meteorology is not, a science largely available in practice. General 

 laws may be laid down respecting the tides, predictions may be founded 

 on those laws, and the result will in the main, though often not with com- 

 plete accuracy, correspond to the predictions. 



And this is what is or ought to be meant by those who speak of sciences 

 which are not exact sciences. Astronomy was once a science, without be- 

 ing an exact science. It could not become exact until not only the general 

 course of the planetary motions, but the perturbations also, were account- 

 ed for, and referred to their causes. It has become an exact science, be- 

 cause its phenomena have been brought under laws comprehending the 

 whole of the causes by which the phenomena are influenced, whether in a 

 great or only in a trifling degree, whether in all or only in some cases, and 

 assigning to each of those causes the share of effect which really belongs 

 to it. But in the theory of the tides the only laws as yet accurately as- 

 certained are those of the causes which affect the phenomenon in all cases, 

 and in a considerable degree; while others which affect it in some cases 



