Before we analyze the difference between a “slave in form” and a “slave in fact” I believe we must establish what each term represents.
Everyone, in one aspect or another, is a “slave in form”. This is a sense of voluntary slavery, or a slavery of necessity. Even though Fredrick Douglas had become a freeman, he still had to labor for a salary in order to maintain himself. This method of being an employee, of being a slave for yourself in return for a steady income, is a “slave in form”. He realized that he still had to work for things in life, but by being his own master he could decide who he worked for and what he did.
A “slave in fact” is the direct opposite of a “slave in form,” and is very straight forward in meaning. A “slave in fact” is just that, a slave. We can infer this when he says “the day had passed forever when I could be a slave in fact” showing us his transformation away from involuntary servitude and into one of freedom.
While similar in appearance, have experience being a “slave in fact”, Fredrick Douglas was grateful to become a “slave in form” because it meant he was his own master, and he worked for no one but himself.