There are some spiritual paths and traditions that deny the existence of the physical world. It is regarded as an illusion created by our projections. This is a common understanding, particularly in the non-dual traditions that originated in India.
The physical world is not an illusion. It is what is here in the moment with you. You can see it, hear it, feel it, taste it, touch it and smell it, and so you can be present with it. Without the physical world, what will you be present with? How will you come out of the mind and the world of illusion?
It is most unwise to dismiss the physical world of form as illusion. What is illusory is the world that we remember or imagine. What is illusory is the world of our ideas, opinions, concepts and beliefs. What is illusory is the world of the human thinking mind and its projections onto the present moment.
But if you are present, you will experience what is really here, free of your projections. It is true that at the deepest level of Presence, the world of form will reveal something hidden within it. Beyond form is the formless. Beyond matter is energy.
At the deepest level, you will recognize the physical world as energy manifesting into form. If you are very present, you can actually see the world of form dissolving into light or pure energy. That is why these spiritual traditions have concluded that the world of form is an illusion.
But to recognize the formless within form should not be a denial of form. To speak of Heaven is to speak of the formless. To speak of Heaven on Earth is to speak of the world of form. Heaven is a formless dimension. Heaven on Earth is Heaven manifested on Earth.
To deny the world of form is to deny Heaven on Earth. And to deny Heaven on Earth is to deny God, for God is both the form and the formless. And beyond the form and the formless, God is, I am, and Thou art.