I know of no study that measures whether the quality of moral debate has risen over the twentieth century. However, I will show why it should have. The key is that more people take the hypothetical seriously, and taking the hypothetical seriously is a prerequisite to getting serious moral debate off the ground. My brother and I would argue with our father about race, and when he endorsed discrimination, we would say, “But what if your skin turned black?” As a man born in 1885, and firmly grounded in the concrete, he would reply, “That is the dumbest thing you have ever said—whom do you know whose skin has ever turned black?” I never encounter contemporary racists who respond in that way. They feel that they must take the hypothetical seriously, and see they are being challenged to use reason detached from the concrete to show that their racial judgments are logically consistent.
James Flynn, Are We Getting Smarter? Rising IQ in the Twenty-First Century, Cambridge, 2012, p. 20
Much of the moral progress of civilization can be understood as the furtherance of concern for “up to usness”, the recognition of its moral importance, and the implementation of arrangements that are based upon this recognition.
Saul Smilansky, Free Will and Illusion, Oxford, 2000, p. 21
It is significant […] that whereas it is easy to find thinkers from different times and places to whom it is intuitively obvious that we have special obligations to those of our own religion, race, or ethnic affiliation, this does not seems so obvious to contemporary ethicists and political theorists. If the strength of intuitions favoring special obligations based on racial and religious affinity is not sufficient grounds for accepting them, then the strength of our intuitions about, say, special obligations based on fellow-citizenship, should also not be sufficient reason for accepting them. Instead, we need another test of whether they should be accepted.
Peter Singer, ‘Outsiders: Our Obligations to those beyond Our Borders’, in Deen K. Chatterjee (ed.), The Ethics of Assistance: Morality and the Distant Needy, Cambridge, 2004, pp. 13-14
It appears to me that the best preparation for original work on any philosophic problem is to study the solutions which have been proposed for it by men of genius whose views differ from each other as much as possible. The clash of their opinions may strike a light which will enable us to avoid the mistakes into which they have fallen; and by noticing the strong and weak points of each theory we may discover the direction in which further progress can be made.
C. D. Broad, Five Types of Ethical Theory, London, 1930, pp. 1-2