Three, by Descartes

 The philosopher René Descartes, halfway between the religious Middle Ages and the rationalist Modern era, decided that you could perceive, whether with your senses or your mind, three different things:

-the res cogitans: your own mind, your own consciousness, experiencing itself. Your senses, your perceptions;

-the res infinita: he called it God. It guaranteed the potency and integrity of the res cogitans.

-the res extensa: the universe, the world.

If this philosophy was an hourglass, the res infinita would be the sand above, dropping its grains through the narrow neck of the res cogitans, so it accumulates below in the form of the res extensa.

Res infinita and res extensa are two sides of the same thing. Both immense, both being looked at by the small eye of the res cogitans. Another way of saying this is: superconsciousness and subconsciousness touch each other and communicate through a back door.