I certainly do not believe that these professional philosophers and scientists are making an obvious logical error. Their error is certainly not obvious or elementary at all, else this discussion would have been over quickly.
The culture of science and philosophy matches the culture of the times. We are living in an increasingly secular culture - so it is no wonder that the majority of scientists and philosophers are secular.
Given our secular culture, perhaps this majority exists because they have been taught to think that the answer to this question is obvious - and so they dismiss it as trivial. In increasingly secular learning institutions, the first cause argument is treated with derision, so modern philosophers learn to deride it. Perhaps they read a few arguments against the first cause argument, believe they have settled the matter, and move on. And so their vast expertise and intelligence is focused on other matters.
You did not mention logical necessity, which I thought was my primary point of strength in my argument. So I wonder if you disagree with my premise - that the first cause must be logically necessary, like math, such that we cannot logically imagine it any other way.
There's a difference between imagining and logically imagining, though they are the same when we are talking of more fundamental things. We can neither imagine nor logically imagine 1+1 equalling 3. Imagining and logically imagining are the same, and equally impossible, in this case. However, when we go towards complexity, these two separate. We (or at least a child learning about math) can imagine multiplication always making a number bigger. But we cannot logically imagine this - 4 times 1/2 is 2.
So it is here. We can imagine God being different, and we may think we can imagine this logically, as a child thinks it logical to imagine that multiplication always makes a number bigger. But we may discover that it was not logical in the end. For physics, I believe it is clear that we can logically imagine these laws to be different. Or do you disagree?
In reality, the laws of physics indeed are what they are. But the fact that we can logically imagine them to be different proves that they are not logically necessary.
As for a set of laws governing all of physical existence, including a multiverse; the conclusion is the same. If this is true, it changes nothing in the argument. We can logically imagine this new multiversal set of laws as just happening to be different without any logical issues. Do you disagree? If not, this shows that these laws, too, are not logically necessary and cannot be the first cause.
I've noticed some assumptions we each have in our definitions of "omniverse" that I think we must confront to better understand each other.
If I understand you correctly, you seem to be assuming that if anything exists outside of our universe, our timespace, then that something must be part of a multiverse, ruled by similar physics. But I am assuming that there is at least the possibility that things exist outside of any physical universes.
You may say that we have no legitimate reason to believe anything outside physical universes exists because we have no scientific evidence that it does. But of course we don't have scientific evidence that it does. Why would we expect to? Science is the study of physical existence. Only philosophy can prove or disprove the existence of anything outside physical existence. The goal of this discussion at the moment is to use philosophy to do just that.
I need to clarify my definition of "mind", which I admit I myself mixed up earlier when discussing a mind with half the thoughts. A mind is not composed of thoughts. A mind is the "I" that has those thoughts. This is what is indivisible, what has no parts, what is perfectly simple. You cannot imagine half of an "I". You can imagine half of the laws of physics because the laws of physics are indeed composed of many laws, each of which can be looked at separately and mentally subdivided. But we cannot logically imagine half of an "I".
You said, "As for simplicity and complexity, would you describe the capability to write a novel, compose a symphony, or design a jet engine as simple? If that's not a "complex" function, what word would you use?"
I would say, "capable". Applying the word "complex" to these abilities only makes sense to us when we think from a physical perspective, from the perspective of brains which have evolved in our physical universe. From the perspective of a mind, these capabilities only show the powers of a mind, and have no bearing on that mind's complexity or simplicity. The colloquial use of simplicity is often used to mean that something is merely composed of few parts. But something that is perfectly simple is unable to be broken into parts - is indivisible.
We know that the first cause must be perfectly indivisible, composed of no parts. Do you disagree with my earlier proof of this? If not, what more likely candidate than a mind, which is uniquely perfectly indivisible?
Imagine there is a serial killer who murdered thousands of women and children because he thought it was fun. He fully knew it was wrong, and he says so, but he delights in the pain of others anyway. He is captured. Imagine that our government has unlimited resources (as God does). Would you really argue that, if we had the resources to do so safely and at no expense to us, we should give this murderer a mansion with delicious food, the latest technology, and build it almost any way he asks for, as long as he is imprisoned safely in this mansion and there is no risk of him hurting anyone outside of it? Do you really believe that this murderer deserves no punishment at all?
The scales must balance not for God's personal satisfaction, but for the same reason 1+1=2.
Justice is inherent in God's nature.
"If a person is honestly, genuinely seeking truth, even if they make mistakes and wind up as a Muslim, or Hindu, or atheist [by no fault of their own], they will still be admitted to heaven."
This is indeed what the Catholic Church teaches. God has set up the Church as the path to salvation. But God can also lead to heaven those outside the Church if this is not their fault (giving them salvation through the Church without their knowing the Church explicitly).
""Outside the Church there is no salvation"
846 How are we to understand this affirmation, often repeated by the Church Fathers? Re-formulated positively, it means that all salvation comes from Christ the Head through the Church which is his Body:
Basing itself on Scripture and Tradition, the Council teaches that the Church, a pilgrim now on earth, is necessary for salvation: the one Christ is the mediator and the way of salvation; he is present to us in his body which is the Church. He himself explicitly asserted the necessity of faith and Baptism, and thereby affirmed at the same time the necessity of the Church which men enter through Baptism as through a door. Hence they could not be saved who, knowing that the Catholic Church was founded as necessary by God through Christ, would refuse either to enter it or to remain in it.
847 This affirmation is not aimed at those who, through no fault of their own, do not know Christ and his Church:
Those who, through no fault of their own, do not know the Gospel of Christ or his Church, but who nevertheless seek God with a sincere heart, and, moved by grace, try in their actions to do his will as they know it through the dictates of their conscience - those too may achieve eternal salvation.
848 "Although in ways known to himself God can lead those who, through no fault of their own, are ignorant of the Gospel, to that faith without which it is impossible to please him, the Church still has the obligation and also the sacred right to evangelize all men.""
-Catechism of the Catholic Church (emphasis mine)
“Nor does Divine Providence deny the helps necessary for salvation to those who, without blame on their part, have not yet arrived at an explicit knowledge of God and with His grace strive to live a good life."
-Second Vatican Council, Dogmatic Constitution Lumen gentium, 16 (emphasis mine)
Likewise, the following statement on morals can be applied to seeking truth as well:
1793 If . . . the ignorance is invincible, or the moral subject is not responsible for his erroneous judgment, the evil committed by the person cannot be imputed to him. It remains no less an evil, a privation, a disorder. One must therefore work to correct the errors of moral conscience.
-Catechism of the Catholic Church (emphasis mine)