Full Idea
By cause of itself, I understand that, whose essence involves existence; or that, whose nature cannot be conceived unless existing.
Gist of Idea
Some things makes me conceive of it as a thing whose essence requires its existence
Source
Baruch de Spinoza (The Ethics [1675], I Def 1)
Book Reference
Spinoza,Benedict de: 'Ethics', ed/tr. White,WH/Stirling,AH [Wordsworth 2001], p.3
A Reaction
Obviously he has God in mind, but might this apply to abstract existence. Can I conceive of the number seven, while also conceiving that there is no such number? Compare Pegasus.