The word hypostasis means underlying state or underlying substance. It is the fundamental reality that supports all else. Neoplatonists argue that behind the surface phenomena that present themselves to our senses are three higher spiritual principles or hypostases, each one more sublime than the preceding. For Plotinus

Plotinus

Plotinus was a major philosopher of the ancient world. In his system of theory there are the three principles: the One, the Intellect, and the Soul. His teacher was Ammonius Saccas and he is of the Platonic tradition...

, these are the soul, being/intellect (Nous

Nous

Nous , also called intellect or intelligence, is a philosophical term for the faculty of the human mind which is described in classical philosophy as necessary for understanding what is true or real, very close in meaning to intuition...

), and the One.