Material objects are known to exist only because we say so. Our senses of sight, hearing, touch, etc., tell us so. Any object we claim to know is entirely a subjective experience. We ourselves are the proof that the world exists.
Do objects exist without our perceiving them? We've read of someone hit by a bus they neither saw nor heard, or the soldier killed by a snipper's bullet he never saw coming.
It appears that objects do exist without our senses having to perceive them. But that does not make them separate. That we perceive objects seems to indicate that we and objects are made of the same stuff.
To be able to perceive what is, implies a common foundation with what is. It cannot be separate if we can see it, smell it, touch it. A common underlying principle must be present.
What is common to all perceptions is consciousness. We tell a friend, "Go to the museum and look at such and such a piece of art." Our friend goes and sees. Doesn't this show that the same consciousness that is in us, is in our friend.
It is obvious that there is one principle behind what is. That principle is awareness. It was present when you saw the art, and again when your friend saw it.
When you saw the art, awareness became conscious of it. When your friend saw it, awareness became conscious of it again. Two people, different times, same aware presence.
That presence is always everywhere aware. It is conscious of all experience. There is nothing separate from it. Consciousness is all there is.