Full Idea
Love is joy with the accompanying idea of an external cause
Gist of Idea
Love is joy with an external cause
Source
Baruch de Spinoza (The Ethics [1675], IV Pr 44)
Book Reference
Spinoza,Benedict de: 'Ethics', ed/tr. White,WH/Stirling,AH [Wordsworth 2001], p.195
A Reaction
This doesn't seem to quite capture the pain that some people find in love.