From Guru Vachaka Kovai:
46 The Supreme is concealed when the world is seen, and conversely, when the Supreme is seen, the world disappears. Both cannot be seen distinctly, as two separate entities, at the same time, [just as] in a carved statue of a dog, the dog and the stone cannot be seen as two separate entities simultaneously.
47 The world that veils the Self through names and forms, and appears to be real, is only a dream-like appearance. If, instead, that very same world gets veiled by the Self and appears as consciousness alone, then, as the Self, it too is real. The world of triputis is only the play of the power of consciousness.
The triputis are the groups of three elements that are essential for perceiving an external world: seer, seeing and seen, and knower, knowing and known.
It's another spin on the idea. Basically, even a reflection in a mirror is real when you realize that you are this mirror itself (substratum).
That's the beauty of these ancient texts. There is no definite answer, and just by thinking about it, you will mature.
