The self-revelation of the "unmanifest God" would give rise to the seven planes of universal manifestation (all visible and non-visible), with their myriad of creatures. One speaks thus of the Unity that gives rise to duality.
Science, on the other hand, with postulates such as the "theory of the Big Bang", tells us that the Universe emerges from the "explosion" of an "initial point" in which matter and energy are infinite, something like a tiny concentrated particle that, when exploited and expanded, gives rise to the joint creation of matter, space and time.
Leaving aside, momentarily, such cosmological models, the truth is that our perception teaches us that everything we are capable of observing, has its opposite (light-darkness, good-bad, cold-hot, masculine-feminine...). And having duality, there inevitably arises the opposition or complementarity.
Duality expresses the idea of opposition, contrast, disagreement, lack..., while Unity would be the expression of fullness and perfection.
Dualistic approaches, surely, because they are the most perceptible, are present in the work of many of the great modern and ancient philosophers. In their maximum expression, they have given rise to the affirmation that there are two supreme principles, uncreated and antagonistic. In their more moderate aspect, they pose the antagonism between God and the world, or between Spirit and matter.
Let us analyze, even if in a superficial way, dualistic Platonic conceptions that, somehow, comprise a great majority of dualistic conceptions, by proposing the postulate of the existence of two worlds: the intangible and eternal world of Ideas and the temporal and sensible world of matter, from which the idea of the body as prison of the soul derives.
Plato's dualistic conception
Like Socrates, Plato believed in the existence of universal truth, but, unlike his teacher, he considered that such universal truths existed outside the sentient world. So, for Plato, the material world was just a reflection of a perfect and ideal world: the world of ideas. With such ideas, Plato impregnated his whole thought with an evident dualism. On the one hand, he records that there is a perfect, immutable world, created before the sensible world (the real world) and, on the other hand, the world of the non-real, the world of appearances and phenomena.
Of course, for Plato, "ideas " are not mere mental concepts formed from the observation of sensitive objects. "Ideas" are immutable and can be grasped only by understanding. For example, the ideas of Beauty, Good, Truth, Justice... would exist by themselves, independent of the concepts with which we want to clothe them. "The ideas", therefore, would be the "real causes", while what we see in our three-dimensional reality would be nothing more than their imitation or distorted reflection.
According to Plato, the world of ideas presents a hierarchical gradation, by planes, at the top of which would be the Good (the supreme Good). However, for Plato and the philosophers of his time, the supreme idea of the Good goes beyond the moral conceptions we usually have on this subject. The idea of Good would be not only the cause of all "good" actions, but the supreme principle of the real.
In The Republic, Plato tries to express the supreme sense of Good, in the myth of the cave. In the sensitive world, we do not perceive the real, but shadows that seem real to us, while "the real" is outside the perception of our senses.
In the Timaeus, the philosopher lets us see that the cosmos (visible and tangible and, therefore, subject to birth and becoming) has its origin in an active and intelligent cause: The Demiurge, the good and wise "god". Now, the Demiurge does not create the world from himself (he is not, therefore, omnipotent), but creates it from three pre-existing elements:
- The ideas (perfect and eternal)
- Chaotic matter, that is, undifferentiated (the original inter-cosmic matter, not assimilable to the "matter" we know).
- The pre-existing space:
"Finally, there is always a third kind, that of the place: it cannot die and it gives a place to all the objects that are born. (Timeo, 51, c)
Thus, the cosmos created by the Demiurge is conceived as a living being, endowed with an intelligent soul (the "Soul of the World"), coming from its creator. However, it is "ideas" that impose on the cosmos a series of geometric structures that matter does not possess in itself. Such basic structures, taken from Pythagorism, would be: the tetrahedron (fire), the cube (earth), the octahedron (air), the icosahedron (water), and the dodecahedron (model of the universe).
For Plato, the Demiurge created the sensible world by imitating pre-existing Ideas (what we could call "thoughts" of God), and sensible objects (forms), which would participate in the Ideas, similar to how a three-dimensional object participates in its reflection in a mirror.
God himself is present in each of the parts
The approaches, both of Plato and of the dualists (Manicheans, Cathars, Gnostics...), raise the eternal struggle between two opposite and irreducible principles, considering that, although the spirit of man belongs to God, his body belongs to the powers of evil. Undoubtedly, such approaches are very much in line with our daily experiences, since we cannot fail to notice, in ourselves, opposed tendencies. Part of our being longs for the noblest, and another part seems to focus, inevitably, on the lowest. Plato, influenced by the Orphics and Pythagoreans, proposed the radical dualism between the soul (of divine origin) and the body. Aristotle (a disciple of Plato), tried to overcome the Platonic dualism, by postulating that the human being is a single reality, a single nature in which "The soul is that which we live, feel and understand" ("De anima",11, chap. 111,13). In other words, the human being does not consist of body and soul, but is a material body with a determining principle, in unity: the soul. In its opposite aspect, we find, in the nineteenth and twentieth centuries, the dialectical materialism of Marx and Engels, where everything, ultimately, is matter and only matter, the essence of the human being contemplated as a set of economic and social relations.
In our opinion, both conceptions arise from the point of view from which the problem is analyzed. If the analysis is made from the corporeality, duality is inevitable. Now, if we were able to analyze it from the soul-spirit, it is obvious that there can be nothing that is not God Himself, so duality would be absorbed by the Unity that presides over the whole Universe. We would conceive how much we are able to perceive, as a unique Being, whose differences, in our irreducible eyes, would be attributable to the limitation of our knowledge and organs of perception.
Now, Non-Duality, at least from our perspective as human beings, does not mean that God, the Whole, is the sum of all that makes up the Universe, but that God himself is present in each of the parts. He is the fire, the spiritual principle, the nucleus, that burns and animates all creation.