LAWS OF MIND. 591 



tliese can be ascertained by observation and experiment. Further, that 

 every mental state has a nervous state for its immediate antecedent and 

 l)roximate cause, though extremely probable, can not hitherto be said to 

 be jjroved, in the conclusive manner in which this can be proved of sensa- 

 tions ; and even were it certain, yet every one must admit that we are 

 wholly ignorant of the characteristics of these nervous states; we know 

 not, and at present have no means of knowing, in wliat respect one of them 

 differs from another; and our only mode of studying their successions or 

 co-existences must be by observing the successions and co-existences of the 

 mental states, of which they are supposed to be the generators or causes. 

 The successions, therefore, which obtain among mental phenomena, do not 

 admit of being deduced from the physiological laws of our nervous organi- 

 zation ; and all real knowledge of them must continue, for a long time at 

 least, if not always, to be sought in the direct study, by observation and 

 experiment, of the mental successions themselves. Since, therefore, the or- 

 der of our mental phenomena must be studied in those phenomena, and 

 not inferred from the laws of any phenomena more general, there is a dis- 

 tinct and separate Science of Mind. 



The relations, indeed, of that science to the science of physiology must 

 never be overlooked or undervalued. It must by no means be forgotten 

 that the laws of mind may be derivative laws resulting from laws of ani- 

 mal life, and that their truth, therefore, may ultimately depend on physic- 

 al conditions ; and the influence of physiological states or physiological 

 changes in altering or counteracting the mental successions, is one oi the 

 most important departments of psychological study. But, on the other 

 hand, to reject the resource of psychological analysis, and construct the 

 theory of the mind solely on such data as physiology at present affords, 

 seems to me as great an error in principle, and an even more serious one 

 in practice. Imperfect as is the science of mind, I do not scruple to affirm 

 that it is in a considerably more advanced state than the portion of physi- 

 ology which corresponds to it; and to discard the former for the latter ap- 

 pears to me an infringement of the true canons of inductive philosophy, 

 which must produce, and which does produce, erroneous conclusions in 

 some very important departments of the science of human nature. 



§ 3. The subject, then, of Psychology is the uniformities of succession, 

 the laws, whether ultimate or derivative, according to which one mental 

 state succeeds another ; is caused by, or at least, is caused to follow, an- 

 other. Of these laws some are general, others more special. The follow- 

 ing are examples of the most general laws : 



First. Whenever any state of consciousness has once been excited in us, 

 no matter by what cause, an inferior degree of the same state of conscious- 

 ness, a state of consciousness resembling the former, but inferior in intensi- 

 ty, is capable of being reproduced in us, without the presence of any such 

 cause as excited it at first. Thus, if we have once seen or touched an ob- 

 ject, we can afterward think of the object though it be absent from our 

 sight or from our touch. If we have been joyful or grieved at some event, 

 we can think of or remember our past joy or grief, though no new event 

 of a happy or painful nature has taken place. When a poet has put to- 

 gether a mental picture of an imaginary object, a Castle of Indolence, a 

 Una, or a Hamlet, he can afterward think of the ideal object he has created, 

 without any fresh act of intellectual combination. This law is expressed by 

 saying, in the language of Hume, that every mental impression has its idea. 



