1) the human brain is a mechanical system made of physical/chemical reactions, like all other systems in nature
I only had to read this point to stop reading.
You're making a case that all systems are the same if they are made up of physical/chemical reactions.
No, I'm not. All systems are different. The point I am making is that agency/intent/consciousness can be interpolated into other natural systems besides the human brain.
I was going to post the definition of 'interpolate,' but I just googled it and the definition doesn't refer to what I mean, which is the opposite of 'extrapolate,' i.e. to make something meaningful in a certain way by applying certain categories to it.
So when you observe a rain cloud and interpolate determinism into it, you do that by recognizing the charge attraction pulling the water molecules together until they condense into droplets and precipitate.
If you observe the brain and interpolate determinism, you have chains of neurons whose dendrites sense axon signals and get triggered to release their chain of action potentials, which stimulates the next neuron to fire, etc. causing patterns of 'lightning' similar to what occurs in rain storms.
With the brain, we can observe these patterns of 'lightning' flashing around inside the brain as conscious experiences, thoughts, decisions, etc.; but with clouds we can't do that because we lack the ability to identify the cloud(s) as a sentient being.
Yet it is possible for humans to look at a condensing/darkening sky of clouds with brewing sounds of thunder accompanying flashes of lightning and say, "that's an angry sky." "that tornado is coming for you," etc.
You can say these are just metaphors, because the sky, a storm, or tornado can't really think and exercise intentional/willful acts, as far as we know, but then again we can only know that human brains do this because we are on the inside of them looking out, instead of being on the outside the way we are with a storm cloud.
The bottom line is this: all things in the universe communicate with each other in various ways or we wouldn't have any knowledge of them. When you stub your toe, it communicates with your brain via your nerves. When a baby is hungry, it communicates with your brain via your ears by crying. When a storm cloud is going to rain down, it communicates with your brain visually and auditorilly.
Does your stubbed toe send out pain signals to your brain consciously/intentionally or is it a deterministic reaction of the nerves to the perturbation? We assume the latter, but at what point does the nerve signal become conscious of itself? When it reaches the brain? If so, why then? Because there are more connections forged between more complex networks of neurons there?
If grey matter is conscious and white matter isn't, i.e. because of the density of connections, then that suggests that the white brain cells are also conscious, just less so because they are more shielded from interaction with other neurons. In fact, probably all types of energetic interactions in the universe are conscious in some way or other, only to lesser degrees than our brains, so we don't acknowledge them as reaching the threshold that we recognize as 'consciousness.'
Nevertheless, all these various systems connect and communicate with each other in various ways, so just as your stubbed toe and the crying baby both communicate with your brain, there must be greater consciousness in the universe where numerous connections occur simultaneously, such as within the sun.
Now you're going to say that I'm calling the sun 'God,' but God is not limited to any one location in the universe. God is the ultimate level at which all things connect and are unified. So we can project consciousness/agency/intent onto all sorts of sub-systems of nature/the universe; but ultimately it all connects and adds up to an overall whole.
God is not just the consciousness of the universe, but the totality of creative power within it. We cannot begin to fathom what it would be like to exist at the level of God, except we can look at our own limited existence and consciousness thereof as being 'made in His image,' meaning we can understand God at higher levels by understanding ourselves at our level(s).
When you reject God, all you're really doing is rejecting all the forms of symmetry and repetition of patterns throughout the universe. Nothing is totally unique and different from everything else, including humans, our minds/consciousness/agency/intent/etc. If we grasp this, it should not be hard to understand that there is an ultimate logic/power/consciousness/agency/intentionality that permeates throughout the unified universe.
We not be able to understand that greater power any more than an ant could understand what it's like to experience life as a human, but if an ant could reflect on its own experience/consciousness/intent/agency/etc., then it could extrapolate that humans have something analogous only more powerful; so the ultimate extrapolation of this ability to recognize generalities among differences is that there is an absolute God of the unified universe of existence.
As such, there is nothing wrong with all the theological work that has been done throughout history to make sense of God and the creation. If good and bad are universal categories, then it makes sense to interpolate them onto every level of the universe, and to describe sub-ultimate agents of goodness as 'angels,' why fallen angels can be called, 'demons.'
Really all it is is a language for describing anything and everything about the universe in terms of agency/intent/consciousness and thus attributing moral logic to it all. In other words, it is a paradigm for making sense/meaning; and as a paradigm there is absolutely no reason for it to be discarded and replaced with some other paradigm.
Materialism/humanism/determinism is not superior to theology. It has borne some good fruits, but it is also limited in numerous ways. As such, it makes sense to maintain and honor traditional religion, as so many people do simply because they have experienced the positive benefits it has had for them and their families/ancestors spiritually as well as materially.