17 



whenever either of these impressions or the idea of it recurs, 

 it tends to excite the idea of the other. The third law is that 

 greater intensity in either or both of the impressions is equiva- 

 lent in rendering them excitable by one another, to a greater 

 frequency of conjunction." 1 The idea of cause, it is stated, 

 is nothing but an indissoluble association, and the entire theory 

 of reasoning, which is founded upon this idea of cause, is 

 reducible to the same basis. For example, ' 'We may define, 

 therefore, the cause of a phenomenon to be the antecedent, or 

 concurrence of antecedents, on which it is invariably and 

 unconditionally consequent." 2 Hence in regard to necessary 

 truths he affirms that axioms are not a priori ; ' 'they are experi- 

 mental truths; generalizations from observation. The pro- 

 position, Two straight lines cannot enclose a space, or in 

 other words, Two straight lines which once have met, do not 

 meet again, but continue to diverge, is an induction from 

 the evidence of our senses." 3 Necessity, understood as the 

 inconceivability of the negative, is but a case of inseparable 

 association. 



Mill, in fact, adopts throughout the psychological stand- 

 point of his father. That he did not accept the position with- 

 out some degree of hesitation and perhaps partial recognition 

 of some of the difficulties involved, may be seen in his form of 

 statement of the subject-matter of psychology, as "the uni- 

 formities of succession, the laws whether ultimate or derivative 

 according to which one mental state succeeds another; is 

 caused by, or at the least, is caused to follow another.' M A 

 realization of the situation is set forth earlier in the same 

 chapter, as follows: 



"With regard to those states of mind which are called 

 sensations, all are agreed that these have for their immediate 

 antecedents states of body. Every sensation has for its proxi- 

 mate cause some affection of the portion of our frame called 

 the nervous system; whether this affection originate in the 

 action of some external object, or in some pathological condi- 

 tion of the nervous organization itself. The laws of this por- 

 tion of our nature the varieties of our sensations, and the 

 physical conditions on which they proximately depend mani- 

 festly fall under the province of Physiology.' ' 



"Whether any other portions of our mental states are 

 similarly dependent on physical conditions is one of those 



KXC. VI, 4, 3. 

 *O.C. Ill, 5, 5. 

 3 O.C. II, 5, 4. 

 4 O.C. VI, 4, 3. 



