One man is merciful, another cruel, by nature; or one is thoughtful and the other thoughtless, by nature. That is a difference of heredity.
One may have been taught all his life that to kill wild things is "sport"; the other may have been taught that it is inhuman and wrong: that is a difference of environment.
Now, the man by nature cruel or thoughtless, who has been trained to think of killing animals as sport, becomes what we call a sportsman, because heredity and environment have made him a sportsman.
The other man's heredity and environment have made him a humanitarian.
The sportsman kills the rabbit, because he is a sportsman, and he is a sportsman because heredity and environment have made him one.
That is to say the "free will" is really controlled by heredity and environment.
Allow me to give a case in point. A man who had never done any fishing was taken out by a fisherman. He liked the sport, and for some months followed it eagerly. But one day an accident brought home to his mind the cruelty of catching fish with a hook, and he instantly laid down his rod, and never fished again.
Before the change he was always eager to go fishing if invited: after the change he could not be persuaded to touch a line. His will was free all the while. How was it that his will to fish changed to his will not to fish? It was the result of environment. He had learnt that fishing was cruel. This knowledge controlled his will.
But, it may be asked, how do you account for a man doing the thing he does not wish to do?
No man ever did a thing he did not wish to do. When there are two wishes the stronger rules.