When we see a mango tree, it is external to us. There is externality. The mango tree is a mental percept. It is a mental concept also. There is no mango tree apart from the mind. We know the existence of the tree through the mind only. There is a mental image in the mind. The image in the mind plus the external something is the mango tree. Even if we close your eyes, we can get at the image through memory.
Our body also is as much external to us as that yonder mango tree. It is also a mental percept or mental concept. The mango tree is external to us with reference to our body only. The mango tree itself is a mere appearance that floats in the Absolute or the One Reality. As the mango tree is external to us from the standpoint of our body, and as the body itself is external to us, the idea of externality of the mango tree or this external universe is blown up now. The term internality also has a false existence only. There is internality only with reference to the externality. If the externality goes away, where is the internality? Both the terms internality and externality are mere illusions, creations of the mind. There is only the solid existence, the One Reality or Absolute behind the so-called internality and externality. That is the Real, Infinite!