HUMAN NATURE A SUBJECT OF SCIENCE. 



553 



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 modi- 

 fications which we shall not be com- 

 petent to explain thoroughly, and our 

 predictions will not be fulfilled accur- 

 ately, but only approximately. 



It is thus, for example, with the 

 theory of the tides. No one doubts 

 that Tidology (as Dr. Whewell pro- 

 poses 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 pheno- 

 mena depends on those causes. But 

 circumstances of a local or casual 

 nature, such as the configuration of 

 the bottom of the ocean, the degree 

 of confinement from shores, the direc- 

 tion of the wind, &c., 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 cal- 

 culated result of general principles by 

 some difiference that we cannot ex- 

 plain, and in unknown ones may vary 

 from it by a difiference that we are 

 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 

 unerring uniformity ; not only, there- 

 fore, is tidology a science, like meteo- 

 rology, but it is what, hitherto at 

 least, meteorology is not, a science 

 largely available in practice. Gene- 

 ral 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 pre- 

 dictions. 



And this is what is or ought to be 

 meant by those who speak of sciences 

 which are not exact sciences. Astro- 

 nomy was once a science, without 



being an exact science. It could not 

 become exact until not only the gene- 

 ral course of the planetary motions, but 

 the perturbations also, were accounted 

 for, and referred to their causes. 

 It has become an exact science, 

 because its phenou)ena 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 ascer- 

 tained are those of the causes which 

 aflfect the phenomenon in all cases, 

 and in a considerable degree ; while 

 others which afiFect it in some cases 

 only, or, if in all, only in a slight 

 degree, have not been sufficiently 

 ascertamed and studied to enable us 

 to lay down their laws, still less to 

 deduce the completed law of the 

 phenomenon, by compounding the 

 effects of the greater with those of 

 the minor causes. Tidology, there- 

 fore, is not yet an exact science ; not 

 from any inherent incapacity of being 

 so, but from the difficulty of ascer- 

 taining with complete precision the 

 real derivative uniformities. By com- 

 bining, however, the exact laws of the 

 greater causes, and of such of the 

 minor ones as are sufficiently known, 

 with such empirical laws or such 

 approximate generalisations respect- 

 ing the miscellaneous variations as 

 can be obtained by specific observa- 

 tion, we can lay down general pro- 

 positions which will be true in the 

 main, and on which, with allowance 

 for the degree of their probable in- 

 accuracy, we may safely ground our 

 expectations and our conduct. 



§ 2. The science of human nature 

 is of this description. It falls far 

 short of the standard of exactness 

 now realised in Astronomy ; but 

 there is no reason that it should not 

 be as much a science as Tidology is, 

 or as Astronomy was when its calcula« 



