The entire premise of slavery is that slaves do not have any rights, least of all to make their opinions on slave policy known. You are judging the man's point by contemporary mores. I am judging the man's point by the mores of that era. By the mores of that era, J.S. Mill is a liberal kook.
But this brings up another point that I often encounter in these discussions. It is this constant effort to judge the past by today's beliefs and attitudes. It seems as if many of you have no ability to put yourselves into the zeitgeist of that period, and see things as the people of that time saw them.
By the mentality of that time, it is axiomatic that a slave owner would not concern himself with the opinions of a slave about slavery. It is a virtual certainty that the slave will be opposed to it, and if the slave's opinion had any weight in the first place, there would be no slaves. Do you think any would volunteer?
Mill was something of a philosopher, and if we paid philosophers, we'd be paying them to ask difficult questions like that, questions that those who believe that some people are born slaves by nature and have no rights don't want asked.
It was at the time a matter of serious economic interest, and nobody was going to indulge philosophical questions on the matter. I'm pretty sure their attitude was "There is too much money to be made, and philosophy be D@mned."
But for what it's worth, as a philosophical matter, Thomas Prentice Kettell puts forth some very interesting philosophical arguments in his book "Southern Wealth and Northern Profits." You should read in that book where he describes the history of Slavery in Europe, (feudalism) and how it gave way to free agency. He put forth some ideas that I had never really considered before, and as a matter of philosophy, I still can't put my finger on how his argument is wrong, though I feel it is.
Speaks volumes about who you are and where you're coming from and how seriously anybody should take you, DL.
Don't make this into an ad hominem. Yes, i'm a horrible person because I note that there is more to the story than we have been led to believe. I should just accept the official narrative of the forces of good conquering the forces of evil, and call it a done deal.
Slavery was abolished throughout the British Empire in 1834.
Slavery was illegal in Britain from an even earlier time, the 1770s or so.
There was nothing anachronistic about Mill's questions.
Moreover, you really miss the point here. There are differences between present and past attitudes to be sure. But the differences within an epoch can be quite great indeed.
What is "our age's" attitude towards your beloved question of transsexuality? The answer is that there isn't any one attitude characteristic of our age. There is a multiplicity of opinions.
So it was with slavery. We can say that expecting 19th century people to take 20th century attitudes to racial equality is anachronistic. Very few people believed in racial equality in those days.
But that doesn't mean that when it comes to slavery we make the slaveholders' view the only characteristic view, normative of its day. Not everybody was a slaveowner. Not everybody believed slavery was right.
Very many people believed that slavery was wrong (in various ways and with varying degrees of conviction). The way people thought in Kensington or Westminster wasn't any less characteristic of the age than the way they thought in Georgia or Alabama.
Mill certain was "ahead of his time" when it came to expressing a believe that colored peoples should have a say in the government that they lived under. I wonder if he'd have shown such consideration to the Indians (or the Irish), but the fact that he could ask the question about the consent of the slaves and publish it meant that the question was conceivable and "askable" in his day.
When people start to justify the Confederacy sooner or later, they often end up minimizing and dismissing the issue of slavery. Sooner or later, you put yourself into the position of the slavemaster. When I was in high school and thought like you did, it was much the same with me. I got over that in time. I hope you will too. It's really too much to be locked into such a way of thinking (or not thinking).