"Now mark another big difference between the natural slavery of man to nature and the unnatural slavery of man to man"---Explain. /Or,/ What difference does the author state between slavery to nature and slavery to man?

This context belongs to G.B. Shaw's essay Freedom. Here the author tells us two types of slavery--one, natural slavery of man to nature and another, unnatural slavery of man to man and also tells us the difference between them. The expression 'natural slavery' means force of nature to which every man must submit. It is nature that forces everyone to eat, drink, sleep for without performing them we cannot servive. But though we cannot but submit to nature's forces, Nature has made her forces pleasant for us. So sometimes we eat and drink too much. And also nature has made sleeping so pleasant that we sometimes find it difficult to get up early in the morning. Marriage and building up families are also instances of our natural slavery. So instead of resenting this forces, we take satisfaction and pleasure in them.

But the second type of slavery that of man to man is very opposite to this. This type of slavery is very much hateful to the author. People of one class make another class's people their slave to fulfill their own sake. No man can be good enough to be another man's master. This type of slavery produces a state of continual civil war called class war between the slaves and their Masters. To the author man to man slavery is a social evil. In this case poor people are the sufferers. In the modern days this has taken the form of conflict between the trades union and employers' federations. In man to man slavery, there is no freedom of time, salary, or tenure of job. All honest governments should take measures to prevent this unnatural slavery but the opposite thing always happens. The government also regulate their country men with laws in the name of freedom. Sir Thomas More believed that this conflict can only end with the abolition of slavery and when every man shall do his share of work with his own hands and not attempt to put it on anyone else.