除神之外不能有也不能设想任何实体

Besides God, no substance can be granted or conceived.

• I.P14

God possesses every attribute (Def.6) and necessarily exists (P11).

• I.Def.6
• I.Def.6.expl
• I.P11

Any other supposed substance would have to be explained by some attribute — but every attribute already belongs to God.

• I.Def.6
• I.Def.6.expl

Two substances with the same attribute are impossible (P5).

• I.P5

Therefore God is the only substance.

• I.P14