For five years he remained on the city's outskirts, writing. In the mid-1660s he moved to The Hague. Substance for Spinoza was not a material reality but a metaphysical entity, the comprehensive and self-sufficient basis for all reality. The modes are transitory, and their existence assumes temporal form. In this scheme, God is eternal, transcending all modal changes.
Existences have their being in time, while essences are outside of time.
Because mortality can pertain only to things subject to the law of time, the realm of essences must consequently be eternal. Every existence has a universal, or essential, character, although to realize this character the existent thing must free itself from the boundaries of its own structure.