You will encounter the concept of non-dualism if you study the Advaita Vedanta. To understand “what is non duality?” you have to understand the concept of the Undivided.
The philosophy of non-duality says that ultimately, in the Universe, everything is ‘one.’ It talks about the existence of One Eternal Spirit. Everything else in the Universe is a part of this Supreme Spirit.
According to non-dual philosophy, the world is not real. It is just an illusion to soothe the mind and the senses.
The Relation Between Non-Dual Philosophy and Ultimate Reality
Because the non-dual philosophy talks about the presence of the One Eternal Spirit, everything else that you see around is an illusion.
The Oneness connects all the living and non-living in the Universe, as opposed to the concept of duality. The latter talks about the duality of existence, that is, how you and the rest of the world are separate entities.
It can be difficult for the human mind to grasp the essence of Non-duality truly. It cannot comprehend that the world is just creating the five senses and that it is not real.
This is why it is crucial to understand the concept of Oneness to understand reality.
To understand ”what is non-duality?” you have to believe there is a higher state of thinking. Once you reach the higher plane, you will realise that everything around you is One.
You have to be one with the Supreme Spirit, and once you know you and the Spirit are one, the contraptions of the worldly life will fall away.
It is then that you realise that the world around you is Maya, and the only reality is your state of Oneness with the One Eternal Spirit.
How to Attain the State of Oneness?
The wise men of the past attained this state of Oneness through meditation. They controlled their mind to stop thinking about the world around them, leaving them calm like still water.
In the process, they discovered that the Self alone was the one true nature. Only when you look within yourself, do you understand the deeper reality.
To better understand ”what is non-duality?” you should practice Adhyatma Yoga. This yoga talks about the practical aspects of non-duality. It is a good starting point if you have recently been introduced to Non-Duality.
With yoga and meditation, you will eventually realise that since you are one with everything else in the Universe, service to the world is service to the Self. To lead a fulfilling life yourself, you have to serve the people around you.
According to non-dual philosophy, since everything you see around you is interconnected to the cosmos at large, you are one with nature. It is the first step to answer the question – “Who am I?”
It will help you understand your place and role in the Universe.
What Is the Ultimate Reality?
Once you start answering the question for yourself, you will realise that the worldly aspects around you are not true. That is not real. Ultimate reality is what you have within yourself; it is the power to connect yourself to the Universe at large.
All the elements that try to keep you away from forming this connection are not real. Reality is not the material possessions you have acquired, but the life force that burns within you.
To attain this supreme state of understanding, you have to focus your mind. Once you become aware of the true Spirit within you, which is the same as the Supreme Spirit, you will know that it is the only actual reality in your life.
How Do These Two Merge?
Your conventional beliefs, habits, and the usual practices followed by society might prevent you from seeing the Ultimate Reality. You have to train your mind to look beyond what the five senses show you.
You have to go beyond the sensory aspects of existence to understand you are not just an individual, separated from the rest of the world. Once you remove that barrier, you will become one with nature. That is the only reality that you will experience.
Once you have grasped the essence of non-duality, you realise that the Supreme Spirit is the only constant. Hence, it is real. Everything else is transient and not actual. As a result, everything else that happens in your life is also not real. Your connection with the Supreme Spirit is the only reality.
Understanding the concept of Advaita can help you solve many existential questions. You become aware of your presence, and you know what truly matters in life. You stop pursuing transient material comforts. You become less obsessed with concepts of profit and loss, and learn to let go. Instead, you start pursuing intellectual pursuits, which enriches your Spirit, connected to the Eternal Spirit.