Morality belongs to Science and Reason, not Religion or Individual Opinion

[Myrddraal]

The goodness and greatness of a man do not justify us in accepting a belief upon the warrant of his authority, unless there are reasonable grounds for supposing that he knew the truth of what he was saying.

I think this is wrong in a subtle but important way. As you said yourself, absolute truth is not necessary. If an Engineer declares that a bridge must not be used, he could be operating with industry standard margins of error. It may be quite possible that the bridge was carry heavy traffic in a storm, but in his professional judgement it is too risky. We defer to his authority because he has studied the problem, and there is a risk of disaster according to his judgement.

You (and Clifford) are both making very strong and detailed arguments to back up what should be obvious to everyone: saying it is so does not make it so. However I think you are approaching this argument with the thought in the back of you head: "God does not exist, therefore dedicating your life to the study of God gives you no authority". If you start with the opposite assumption, then a clergyman has a great deal of authority, as he has dedicated his life in search of the truth of God's intentions. True, study of God is less rigourous almost by definition, in that it is harder to test empirically, but that does not mean that clergymen (many of which are much more intelligent than myself, and possibly you too) do not approach the problem with the same rigourous attitude. So dare I say it, the implicit attack on organised religion and the clergy boils down to the question of wether God exists or not, which, let's face it, we're probably tired of arguing about in the Backroom. Of course if we take the Christian belief, then Jesus has moral authority beyond that which any man can obtain without ceasing to be man, but that's an aside.

Can we defer to the authority of clergymen? Unfortunately not, which is part of the point of this thread.

I guess that my argument is that your case is strong to the point of undeniable as it builds up the argument that self-deception does not justify deception, but it breaks down here. The fact that an Engineer studies Engineering and a clergyman studies God does not give one more authority than the other in their given field, unless you begin by saying that the study of God is invalid. Saying that religion is less rigorous by its nature isn't enough to make this point imo, you are jumping to a conclusion without filling in the gap (does God exist).

I guess that's what my point about the physics denier is: as a physics denier I cannot deny your authority in matter of physics, even though I don't believe that physics is real. Now get your tongue around that
So as an atheist, you can say that the Bible does not affect your morals, but you cannot use the same argument to denounce dogma and the 'moral authority' of clergy for those who do believe.

At the end of the day, it makes very little practical difference. Most theists believe in a benevolant God who wants the best for humanity. Most people believe that what is 'right' is what is 'best' for 'society'. We (both atheist and theist) can certainly apply scientific methodology in exploring (and modelling/codifying?) what this means.

As for filling in that gap, perhaps another time, and as for the core of your argument, it's very true, almost obvious when you explain it, but also very easy to loose sight of.