Indian thinkers when studied the world they found two things – one is real other is unreal – they called it sat and asat.
There are two aspects of the world one is changing – ever changing and another is unchangeable. Shankaracharya says – every moment it is becoming something else. Change is the characteristic of this external and much of the internal world and anything which changes moment to moment vedanta calls it unreal. It exists but it is unreal, it appears but it is unreal. The nature of this manifested universe, a universe which one experiences with the five senses, is that, it is constantly changing, and therefore is unreal.
Whatever changes is unreal. Then where is the reality? Vedanta says there is the changeless reality beyond the sensory level; sat is real, it cannot be nonexistent. You come to the world of reality which is unchanging, infinite and eternal. This distinction was made very early in our philosophy. This becomes more and more confirmed when you study modern physics dealing with matter or modern biology dealing with living systems. For example your body changes in every few years, everything in the body has changed, yet you say i feel, i am the same person. Some sort of unity is there in this world of change. Man alone can discover it.
Mandukya karika a vedantic text gives a beautiful definition – “that does not exists in the beginning and in the end, and appears only in the middle is called unreal”.
Then what is real- that which exists in past, present and future is called real. It is always there. Is there such a real, “yes” says Vedanta, and that is the search of philosophy everywhere in the world.
adopted from writings of Swami Ranganathanandaji.