Life, Liberty, Property, and Happiness

Why does a parent have the moral right to forcefully control his children, but government does not have the right to forcefully control its citizens? Why is is permissible to enslave animals, but not human beings? What is the fundamental difference between animals and man, or children and adults?

What is the definition of a child, and how do we arrive at that definition? Why is it moral to be biased against animals that have a desire for life, freedom and happiness? Why do we insist that all men have a natural right to these things, a self-evident right, but animals do not? Do we imagine that if we found a method for honest communication, animals would not insist that they too deserve these rights?

What happens when machines become so complex that they too demand the same rights?

This is a continuation of this discussion, which went to some length at the Cafe Hayek blog.