Not true? Please, please post about that. Not about moral progress etc, but how you have come to hold that any moral belief can be an objectively true belief.
I wouldn’t want “enslave him” to become a universal law (Kant I)
Enslaving people treats them as means, not ends (Kant II)
I wouldn’t want to become a random member of society that permits slavery (Rawls)
I wouldn’t want “enslave him” to become a universal law (Kant I)
Enslaving people treats them as means, not ends (Kant II)
I wouldn’t want to become a random member of society that permits slavery (Rawls)
etc