High Quality Content by WIKIPEDIA articles! Sociaal-Liberale Partij (SLP) (Dutch for Social Liberal Party) was a Belgian Flemish political party formed after dissolution of the moderate nationalist People`s Union (Volksunie) party. Prior to 19 April 2008 it was known as Spirit, and intermediately as Flemish Progressives (VlaamsProgressieven). The party fused with Green! in the end of 2009 thus ceasing to exist.