Advaita Vedanta is one of the three main schools of Vedanta Philosophy. The Vedanta philosophy is based on the Vedantas, the Upanishads of the Vedas. They are the oldest of the religious literature existing today and are more than 5000 years old.
There are three main schools of Vedanta philosophy:
Dvaita or Dualism: In this school, the Absolute or Brahman and the world including our soul are considered to be two separate and distinct realities with no connection between the two, Brahman being the higher reality.
Vishista-dvaita or qualified monism: In this, the world is considered to emanate from the Absolute Brahman and the world is an effect of Brahman, like a spider’s web. Thus, although the world emanates from and is a part of Brahman, it is a lower form of Brahman.
Advaita o Monism: This is the final school of Vedanta, and is considered the most intellectual school. In this the reality of the world is denied and the only existence is that of Brahman.
In Advaita Vedanta, Brahman is considered to be the root of both the objects of the world and the subject, our consciousness. The reality of both the subject and the object is denied and the only real existence is that of Brahman.
When considering the objects of the world, all the phenomena of the world exist in time and space and are subject to the laws of causality. The ancient sages through logic came to the conclusion that there was no fixed time, since we could not define time itself absolutely. Space could not be defined either, and since objects and causal phenomena exist in time and space, all objects have only a relative reality. In modern science as well, we know from the law of relativity that time and space do not have absolute reality, and because of this, causality also does not have absolute relativity since for an observer traveling close to the speed of the light, the cause and effect of any phenomenon would be very different from the cause and effect seen by an observer at rest. The simultaneity of events would be different for any phenomenon for different observers. Therefore, science has confirmed Advaita Vedanta in this regard, that objects and phenomena have only relative reality.
But Advaita says that things cannot have only relative reality from beginning to end. Since there is the existence of the world, there must be an absolute reality at the base to support this relative reality.
This absolute reality at the basis of the existence of the world is Brahman.
In the same way, Advaita Vedanta says that our individual consciousness at the surface level has only a relative reality. Our individual consciousness is nothing more than a stream of thoughts and sensations that follow each other, and there is no reality at this level. But there must be an absolute reality at the base of this consciousness, otherwise we would not have had consciousness.
This Absolute reality at the base of our consciousness is Brahman.
Thus, in Advaita Vedanta, both the objects and the subject have only ambiguous reality and no true existence, and only the Absolute Brahman as the basis of both has true existence.
The goal of spirituality is to experience this state of existence in Brahmanity. By stopping the stream of thought-feelings in our consciousness, we can still our consciousness and then we will exist as Brahman itself, which always was and always will be our true identity. This is the ultimate goal of Advaitin.