Without God, there is no such thing as an objective basis for morality. Kant recognized that this was essential: "The end here is inescapably fixed, and according to all my insight there is possible only a single condition under which this end is consistent with all ends together and thereby has practical validity, namely, that there be a God and a future world; I also know with complete certainty that no one else knows of any other conditions that lead to this same unity of ends under the moral law."

Even with God there is no agreed way of determining what or which morality, if any, is objective. Look at the differences between the ethics of (say) the monotheistic religions of Judaism, Christianity, and Islam let alone of separate strands within them. Even within a religion, different people's consciences offer conflicting guidance.

I don't think that, at the level of generality at which the question has been formulated, it can be answered illuminatingly here. Answers are likely to cover a wide variety of views, none of which can be firmly vindicated.

@GeoffreyThomas. Agreement is irrelevant. What makes it objective is that there is only one correct answer; i.e., every moral act either conforms to God's will or it doesn't. The truth can be found by anyone who seeks it with genuine sincerity and humility. Unfortunately, that rules out almost everyone, because only by God's grace can we find such humility.

@PédeLeão I think God's will may want us to make choices between options that are not clear-cut. This would allow us freedom. I think one could ground morality in what is good for a group, however, I don't know enough to answer this question except as an opinion.

@FrankHubeny. Sure, we have to make choices and sometimes it's hard to know what we should do, but that doesn't imply that the objectivity of what is morally right is a question of opinion or agreement. Rather, it is an ideal to be strived for, as Kant said, "Thus only in the ideal of the highest original good can pure reason find the ground of the practically necessary connection of both elements of the highest derived good, namely of an intelligible, i.e., moral world." (A811/B839)

@PédeLeão If God is the one to establish an objective basis for morality, does that mean that those who are not religious or do not affiliate themselves with God do not have any objective basis for morality? That is, are they only guided by the primitive instincts that they possess?

@ssharma. God created us all with a basic sense of morality. For those who reject God, it's really a question of justice so that, on the day of judgment, they may be left without excuse for their transgressions. See Romans 1:18-20.

So, in essence, for those that reject God, there is no clear-cut sense of morality?

@Pé de Leão. Careful : there can of course be objective truth without agreement. I would not deny anything so obvious, so well-attested by experience. Nor do I believe that agreement can, save in exceptional circumstances, create truth. The problem is that if 'every moral act either conforms to God's will or it doesn't', God appears to speak in different voices to different people. That problem is aggravated if we have no means of knowing who has found the truth by God's grace and who hasn't.

@GeoffreyThomas. The diversity of opinion isn't due to God speaking "different voices"; rather, it's due to mankind employing different approaches to deal with the incoherence that results from not really wanting to know the truth. Like I said, we do have the means of discovering the truth, but very few actually want to with genuine sincerity and humility. Those who do recognize the work of Christ as the signature of the one true God.

@Pé de Leão. I didn't say that God speaks with different voices but that God appears to do so. How do we tell the real from the apparent voice of God ? St Augustine recognises the fact and bindingness of erroneous conscience; he acknowledges that an erroneous conscience can arise even when the moral agent has sincerity and humility. Erroneous conscience can cause a diversity of moral opinion, then, even without the moral failing of 'not really wanting to know the truth'.

@Pé de Leão. I need to correct with apologies an error about conscience. Augustine does not believe that an erroneous conscience is binding; it is Aquinas who takes this view.

@GeoffreyThomas. God has promised that those who seek will find. There's no need to try to analyse it any more than that because, in the end, it is God who accomplishes the task, and He's more than capable of revealing the truth to whoever He chooses to reveal it.

@Pé de Leão.W. Lyons: 'for Aquinas,conscience is the whole internal conscious process by which first principles of moral right and wrong,learnt intuitively by synderesis,are applied to some action now contemplated in order to produce a moral verdict on that action. . [W]hile synderesis, as a fundamental intuitive capacity of the soul given us by God, could be said to be morally infallible, the deductive processes of conscience, whereby these first principles are syllogistically applied to some practical situation, could go wrong. Anyone ... can make mistakes in logic or errors of judgment'.

@Pé de Leão. The article is : W. Lyons, 'Conscience - An Essay in Moral Psychology', 479-80. Aquinas, De Veritate, 16.2. The consequence that errors of judgement (the deliverances of erroneous conscience) are binding is developed from Aquinas' views by Eric Darcy, 'Conscience and its Right to Freedom', 1961. Excuse me if you are already aware of all this. Best - GT

@Pé de Leão. I can accept that but still ask, when there are moral disagreements, which are a fact of life, what are we to do as interacting agents, social beings, if one says 'X is right' and another says 'X is not right'? We have to make group decisions - we have to act - without knowing to whom God has revealed the truth. Another point - Aquinas's - is that God can reveal the truth but we can still make errors in good faith about what the truth requires.

@GeoffreyThomas. We go to the Bible with prayer and humility and seek the truth like the Bereans did (Acts 17:11). We're only human, so we do the best we can with what we have.

@Pé de Leão. And being only human, finite in knowledge and intelligence, we will disagree. Will the NT decide the issue over contraception or abortion ? I don't think so. But if I can offer a neutral remark, I think you need a theory of self-evidence. How do you know that God has really revealed the truth about some moral matter to you as opposed to its only seeming to you that God has done this ? How can you tell that X is really self-evidently a divine command or inspiration or only appears to be ? And how do I know which is the case when my conscience offers conflicting guidance to yours?

I, personally, think that this comes down to a good skeptical argument about the epistemology of moral facts (agreement with God's will) vs. dogmatic faith. Neither will ever be able to convince the other.

As far as I understand the argument of @PédeLeão, all we can do is doing the best we can to follow God's will. As finite beings, we will err from time to time. Problem being, this berefts the whole idea of accordance with God's will as a measure stick for moral behaviour: We will not and never know whether what we think best is good.

@GeoffreyThomas Just because we make mistakes doesn't mean that we can never be certain. Some issues, like abortion, are very clearly against God's will. Therefore, I strongly disagree with @PhilipKlöcking's comment that "We will not and never know whether what we thing best is good."

@Pé de Leão. Nothing can be clearer than the seriousness with which you take the issues we have been discussing. But it is equally clear that neither is making any impression on the other. I have made all the basic points that seem important to me. Others may want to comment further on your views but I don't think you will gain anything from more discussion with me. So I will bow out and wish you well in your reflections. I appreciate the time you have given. Best - GT