Cause of Character Traits --- According to Aristotle

   What makes for an unjust person?  What causes the character 
   trait of "unjustness"?  According to Aristotle this character 
   trait is caused by a person repeatedly doing unjust acts. 

   What causes the character trait of profligacy?  According to 
   Aristotle this character trait is caused by a person spending 
   his time in drinking, etc.. 

   What causes the personality trait of carelessness?  According 
   to Aristotle people acquire this character trait through 
   leading disorderly lives. 

   According to Aristotle:  "Activity in a certain thing gives a 
   man that character --- dispositions are attained through 
   actually doing things." (Ethics, Book III; The Philosophy of 
   Aristotle, p.324) 

   Also, according to Aristotle, a man who has become unjust or 
   profligate or careless, cannot stop being so just by wanting to 
   stop.  Just as a man who is ill cannot become healthy just by 
   wanting to.  The unjust or profligate or careless got that way 
   through actions taken of their free choice but once they have 
   become that way it is not possible for them to be otherwise. 

   The following excerpt comes from Aristotle's Ethics, Book III 
   (see The Philosophy of Aristotle, p. 324, 325): 
    
   "But perhaps the man's character is such that he cannot take 
   care.  Well, people themselves are responsible for getting like 
   that, through living disorderly lives:  they are responsible 
   for being unjust or profligate, the former through evildoing, 
   the latter through spending their time drinking, and so on.  
   Activity in a certain thing gives a man that character;  this 
   is clear from those who are practicing for any contest or 
   action, since that is what they spend their time doing.  Not 
   knowing that dispositions are attained through actually doing 
   things is the sign of a complete ignoramus. 

   Also, it is absurd to say that the man who acts unjustly does 
   not wish to be unjust (or profligate, when it is a case of his 
   doing profligate acts).  If a man does acts, not in ignorance, 
   that will make him unjust, he will be voluntarily unjust.  
   However, he will not stop being unjust and become just merely 
   by wanting to.  Nor does a sick man suddenly become healthy.  
   It may happen that his illness is voluntary because his way of 
   life is unrestrained and he disobeys his doctors.  At the 
   start, it was possible for him not to be ill;  but this is no 
   longer so, once he has let things go.  It is like the man who 
   has let the stone go and cannot recover it.  However, letting 
   it go was in his power, since the principle of action was in 
   him.  Similarly with the unjust and the profligate:  at the 
   start it was possible for them not to become like that;  that 
   is why they are voluntarily so.  Once they have become that, 
   however, it is impossible for them not to be so." 

   In other words, according to Aristotle, character traits such 
   as unjustness, profligacy, carelessness, etc. are just habits 
   (they are not inherited).  They are formed (as all habits are 
   formed) by actions, which being often repeated, become fixed 
   personality patterns.  There is a proverb that says something 
   like "Habits begin as threads and end as cables".  Bad habits 
   enslave people and that is what happens with unjustness, 
   profligacy, carelessness, etc..  The characters of most people 
   are formed when they are children.  The habits they acquire 
   when they are in the process of growing up are those that 
   determine their life-long character.  One's character and 
   personality is pretty much "set" in his younger years by the 
   choices he made as a child (my view).