When I was an atheist, my position was what I will call Newtonian, by which I mean "“I have not been able to discover the cause of those properties, and therefore I frame no hypothesis."
Only long after did I see the illogic in this stance. Allow me to explain.
As a matter of pure logic, the fact that my human mind was capable of comprehending and following the laws of logic, that is, of perceiving facts and drawing conclusions and acting on them, forced me to conclude
1. that objective reality existed
2. the human mind could (at least in this case) apprehend it
3. the laws of logic were independent of the subject matter, that is, were formally true, which meant, true independent of material circumstances
4. I could choose to accept or reject the conclusions of logic, that is, I had free will
5. It was morally wrong of me to accept the illogical and untrue over the logical and true. Thoughts and words that were untrue are called lies, actions that were immoral are called vices.
These five sentences could not all be true unless it were also true that objective morality existed and that I had a free will to choose between them, to select good over evil, honest over dishonest, reason over unreason.
So far, in none of this, did I see a necessity for a supernatural sovereign creator to create or maintain these things. Without going into details as to the steps, similar parallel reasons required me to conclude that cause and effect governed the material world perceived by the five senses, such that any effect which had no seen cause must have an unseen cause. Moreover, in using words and symbols to refer to things, both objects of perception and objects of the mind, required me to conclude that essential properties differed from accidental, necessary from contingent. Likewise, I was required to concluded that beauty and ugliness in essence were objective, albeit their accidental properties were matters of taste, which depended on culture, upbringing, and training to appreciate the forms. I rejected subjectivism in metaphysics, physics, ethics, politics, and art.
As for where and how objective morality arose, and why it had authority, and why the mind and psychology of man was ill suited to live a life without vice, despite that this was both good and generally good for him, I held this to be an unanswerable question, like asking whence and how objective geometry arose, or the laws of logic. I held that the laws of morality were merely the laws of logic applied to human action: when the act is the essential, and the specific fact that it is me rather than you, or my faction rather than your faction, was an accident. The Golden Rule was the Law of Identity. A is A. If the thing is evil when you do it to me, it is evil when I do it to you, all other factors being equal.
Finally, objective morality necessitates the pursuit of virtue. The obvious miseries that flow from the pursuit of vice are too obvious to mention. But virtue is difficult, and requires more than a one-time effort of will. We are not computers that could simply be programmed not to lie and cheat, because the luxurious temptation and temporary rewards for dishonest and dishonorable behavior are so strong and frequent.
Therefore morality requires discipline, that is, the habitual effort to govern the appetites and passions and bring them into subjection to nature. It is merely illogical to crave to fly like a bird or live as long as a redwood. Humans cannot do that. It is merely dishonorable to vow eternal fidelity to a mate and then take a second wife, or mate without marriage, or hire a harlot. It is merely unnatural to couple with children, animals, corpses, or members of one's own sex, for the reproductive passion here is aimed at what is essentially not merely indifferent to reproduction, but antithetical. No man, and no society, can affirm monogamy and sodomy in the same sense at the same time.
In all of this reasoning, I held that attributing the cause to a supernatural source did not answer the question, but merely put it out of reach. Having no information about the supernatural world, even whether it existed or not, one could frame no hypothesis.
However, all this carefully engineered structure of conclusion came crashing down once I realized that this moral system I had deduced without reference to the supernatural could not answer the natural question whether morality was based on pursuit of self-interest rightly understood, or adherence to those duties that arise from nature, particular the duties of fatherhood. If morality is objective, is in necessary for human wellbeing, what moral code should a father rear and train his children to uphold? Hedonism or stoicism? Sodomy or monogamy?
Without God, these are questions where reasonable men can differ. But in reality, there is no reasonable argument favoring sodomy or hedonism.
Which means that there must be an objective law concerning not merely morality, but matters of judgment, and this requires an objective, that means, an universal and superhuman, lawgiver and judge. And this all men know to be God
.