THE CAUSATION OF DISEASE. 1 75 



cause has no corresponding practical disadvantage. It is suffi- 

 cient for us to know that the same results always follow from 

 the same conditions, and it becomes the business of the 

 scientist to investigate the order of phenomena, to discover as 

 many laws as possible, so that he may know what will be the 

 result of any given conditions. 



And this is the task which the pathologist has before him. 

 He inquires into the laws which govern disease, but, be it 

 remembered that, in stating the cause of disease, he, in the 

 last resort, can do no more than enumerate those conditions 

 out of which it has arisen. 



The conditions from which different results follow may be 

 spoken of as material conditions — conditions of matter. For, 

 although we have no absolute knowledge of the existence of a 

 material world (since we can know of nothing apart from our 

 own mental states), such an assumption is, to say the least, 

 convenient, and aids us in the practical concerns of life. 



The material conditions embrace : kind of matter, quantity 

 of matter, disposition of matter, motion of matter. Every 

 result of which we have any knowledge may be brought about 

 by a modification of these material conditions. Even mental 

 phenomena may, for all practical purposes, be said to follow 

 from them, for, although the exact relation between mind and 

 matter surpasses all understanding, of a relation between the 

 two there can be no doubt, inasmuch as every mental sequence 

 is accompanied by a physical sequence, and any disturbance in 

 the latter causes a corresponding disturbance in the former. 



In seeking, therefore, the cause of disease, our object must 

 be to discover the material conditions out of which it has 

 arisen ; and, further, to formulate as many laws relating to 

 disease as possible. 



Disease is a vital process. It may be defined as an " ab- 

 normal mode of life.'*' This definition assumes a perfect 

 knowledge of what constitutes normal life, but it is no easy 

 matter, as we shall see in a future chapter, to say what is 

 normal life. We are, nevertheless, justified in assuming an 

 ideal or normal life. Disease may then be very readily 

 defined as an abnormal mode of life. 



