I know that it is shocking for Trinitarians to ask this question, but it seems to me that monotheism, pure monotheism is more primitive. While Trinity is of less primitiveness and of less common sense.
Primitive and common sense means near to the pure heart or near to the original state or pureness or innocence or innateness.
So, the question is: is pure monotheism of less primitiveness and of less innateness than Trinity or Tritheism?.
It must first be stated that Trinitarianism is in fact monotheism. In Trinitarian belief there is only one God. However the nature of that one God is that he exists in three persons. But it is one of the fundamental doctrines of the Trinity that Trinitarianism believes in a single God.
Monotheism is not more primitive than polytheism.
It is a matter of historical record that ancient religions had many gods, and that monotheism exists only among more recent religions.
Is non-Trinitarian monotheism more "common sense" than the Trinity?
It depends what you mean by common-sense, but possibly. The concept of the Trinity is difficult to understand, and it appears to contradict our normal understanding of things.
However being less "common-sense" does not make it untrue. Many things in our world are not very "common-sense". It defies common sense that something can be both a wave and a particle, or that it can have an undefined position. Yet quantum physics tells us unquestionably that both are true. Quantum physics is less "common sense" than classical physics, but it is true.
Likewise it defies common-sense that something may get heavier as it goes faster, or that time moves at different rates for different things. Yet Relativity tells us that both are true. Relativity is less common-sense than Newtonian physics, but it is true.
TL;DR: According to Christianity and the experience of saved people TODAY, what fallen (non-saved) people consider "primitive" and "common sense" is no longer the same as the people in the original state of purity and innocence. So to answer your question, it depends on who you ask. To believers Trinity makes more common sense, but to the fallen / unsaved, who can predict what their corrupt reason say?
The fuller answer below is for Trinitarian believers who want to defend that our concept of Trinity actually explains more of the true nature of the original / redeemed human heart.
I'm in no way saying that just by having "common sense" people can discover Trinity on their own without God's history of revelation recorded in the Bible. But after their reason has been "baptized" Christians should recover the original state of purity and innocence and only then will they discover that Trinity makes more "common sense".
Christians believe God created human being in a state of purity and innocence. What does it mean? It means that the human heart, through experiencing the world in what we are doing, thinking, and making is longing to relate to God. The mind wants to glorify God. The emotion is naturally overflowing with joy when contemplating the beauty of God's creation. The body wants to give what we create to God as an offering, like a child who like to show her art project to her daddy, who thanks her daddy for supplying her with crayons and art paper. That is the state of purity and innocence which the doctrine of Trinity tries to restore us to.
But we live in a fallen world. There is a deep shadow obscuring this purity and innocence. Human beings now want to make our own God, by making our own ethical standard of right and wrong, and by casting God in our fallen image. So what's common sense for unsaved people should be taken with suspicion.
Trinity does not cease to be Monotheism. There is still one God and one Universe which does not contain the one God. But is this conception sufficient to capture all the longing of the human being created in the state of purity and innocence? There is no inherent relationship in having one God that is aloof from creation, the "watchmaker" God created by the fallen enlightenment era philosophers. Even Plato's demiurge + world soul was better, and Neoplatonism was more satisfying as a religion compared to the modern solitary conception of human as orphans entirely "trapped" in our individual body unable to relate to each other and to the creator. Very sad and tragic ! What Trinitarian conception of God brings is to "relationalize" this Monotheistic God unfortunately mangled by philosophers.
It's a logical fallacy to insist on being able to explain the "logic" of the Trinitarian "One God in Three Persons" before you can believe God as Trinity. Even the Monotheistic God does NOT have to be fully explained in order to be believed, so why compare the more difficult way to construe Trinity to a simpler "more primitive" Monotheistic conception that could very well turn out to be less than real? We need to learn from the more humble Aristotle and Plato who acknowledged some unexplained aspects of God rather than the modern philosophers who at the end of the day reduce God to what they can define. I hope you see the arrogance and absurdity of some philosophers who value logical consistency more than reality. On the other hand, philosophers like St. Aquinas or St. Anselm realize the limit of their philosophical endeavors and by faith see within their hearts the reasonableness of Trinity because they have a more pure and innocence concept of reason. That's why the medieval philosophers see philosophy as a handmaiden to theology as opposed to some modern philosophers who see theology as an obstruction or myth to be destroyed.
Christians believe that by having Holy Spirit in our hearts we are able to participate in the Trinitarian love relationship within the Godhead, following the example of Jesus who while being fully human was able to live this state of purity and innocence before God the Father and having the Holy Spirit in His heart. That is why in order to recapture the pre-fall state of human heart we need to follow the example of Jesus. We can start by acknowledging him to be the Son of God, the first step to see this Monotheistic God as a Trinity.
The use of the phrases, ‘more primitive’ and ‘pure monotheism’ are interesting as they seem to be equated with ‘more simple’, and imply that more simple ideas are more likely to be true. DJClayworth has already given a good answer to that, giving examples of modern, complex ideas that cannot be held to be untrue just because they are modern and complex.
I would answer that ‘primitive’ monotheism maintains a simple Theos, easy to understand from a human point of view, but that later monotheism as developed within the pages of the Bible, particularly the Christian Greek scriptures, shows a complex Theos. It is less likely that a simple theology of God is more likely to be true than a complex one. That is because of the very nature of the Being of the one God, some of which he has chosen to reveal to humanity over the centuries. The more humanity learns of God and observes his dealings with us, the more in awe of him we should become, realising that nobody can expect to plumb the depths of God’s Being this side of eternity.
Secondly, your use of the phrase ‘common sense’ prompts me to share points about that, to illustrate that what one person might consider to be ‘common sense’, another person no longer does. Indeed, there is an apparent absurdity about much ‘common sense’ these days. It used to be common sense to say that only women can give birth but that is no longer the case; and where did common sense go when schools were required to get parental consent to administer sun lotion or a plaster to a child - but could not inform the parents when their daughter became pregnant and wanted to have an abortion? Times have changed and, with it, the perception of what common sense should now be. This shows how fluid and ephemeral ‘common sense’ is, that it is not a safe measure to apply to matters of truth for humans, let alone to matters of truth regarding God.
The Trinity doctrine was never an attempt to clear up all mystery about the Being of God. That will always remain a mystery this side of glory because we are finite and God in infinite, but at least it is expressed in such a way that we can see wherein the mystery lies. That is more sensible than going for a simplistic theology that presents a simple God. The one Being of God is complex, not simple, and common sense actually dictates that that is just what we should expect. Let’s not throw out the baby with the mucky water of polluted Common Sense.
It is common sense to listen to what God has to reveal about himself rather than to concoct a theory out of one's own human knowledge and experience, or to follow what other human beings have dreamed up within themselves.
In the nature of God, he is eternal and spirit.
Thus he cannot be discovered by human means. He reveals himself. It must be so.
Thus one must discover, not what one thinks within oneself, not what other humans think, but one must seek and discover what God has revealed about himself.
So, forgetting all human terminology, it is simply common sense to seek out, to discover, to find out - what God has revealed about himself.
Any other way is just not sensible.
Is 'pure' monotheism of more primitiveness and pureness than the Trinity is?
The biblical answer is Yes.
The first person created by God is Adam, and Adam knew only One God and He is the Abba Father.
Then the LORD God formed man from the dust of the ground and breathed the breath of life into his nostrils, and the man became a living being. (Genesis2:7)
So, if you're talking about primitiveness, the answer can be found in Adam because he is the first primitive person that existed who knew God existed as One or simply monotheism.
Your specific question states;
Primitive means near to the pure heart or near to the original state or pureness or innocence.
The answer to this can also be found, in Adam and later on Eve, both Adam & Eve were created in the state of purity and innocence and they only knew One God.
"Then the LORD God made a woman from the rib he had taken out of the man, and he brought her to the man. 23 The man said, “This is now bone of my bones and flesh of my flesh; she shall be called ‘woman,’ for she was taken out of man.” (Genesis2:22-23)
So, based on biblical history if we look at Adam & Eve it would seem that monotheism is the primitive knowledge of created man. But wait, before Adam & Eve was created the monotheish God had spoken first this words;
Then God said, “Let Us make man in Our image, after Our likeness, to rule over the fish of the sea and the birds of the air, over the livestock, and over all the earth itself and every creature that crawls upon it.” 27So God created man in His own image; in the image of God He created him; male and female He created them. (Genesis1:26)
The monotheism who created the first man Adam revealed Himself as existing in "plurality" meaning, the monotheism existed primitively not as one but in plurality and the Christian Faith understood this as the Most Holy Trinity.
