Why do some people say that this world actually exists only within you?

There is a cup in front of you.
You drink water, it’s a water cup; you smoke, it’s an ashtray; you arrange flowers, it’s a vase.
The cup itself is actually nothing in particular,
It is whatever you make of it.
The problem begins the moment you start “defining what it is.”
If you insist on your definition and others don’t agree, you start to argue;
Arguing leads to emotions, which is called worry;
Accumulated emotions turn into judgments, which is called bias.
You think you are fighting against others,
But in reality, you are just constantly reinforcing your own internal explanations.
So, much of the world you see isn’t “what it truly is,”
But “what you perceive it to be.”
Those obsessions, emotions, and biases are not fundamentally imposed by the outside world,
They are built step by step by yourself.
Looking at it from a different perspective,
Of course, the world has others, but everything you experience ultimately only happens within you.
Originally, there is nothing—where could dust settle?
The more effort you put in, the luckier you become.