Full Idea
He who lives under the guidance of reason, desires for others the good which he seeks for himself.
Gist of Idea
A rational person will want others to have the goods he seeks for himself
Source
Baruch de Spinoza (The Ethics [1675], IV Pr 51)
Book Reference
Spinoza,Benedict de: 'Ethics, Improvement of Understanding, Letters', ed/tr. Elwes,R [Dover 1955], p.222
A Reaction
Obviously a very Kantian idea. It implies that all rational people desire similar goods, but it is rational to collect stamps but not want other people to do so as well. I don't think you should want what I want for Christmas.