The original nobility: patricians and knightsby Jan-Olov von Wowern
By "nobility" I refer to that class in society which once had hereditary political, financial and social privileges guaranteed by law. By "original nobility" I follow German (and now internationally accepted) definition and refer to those families who were ennobled (or generally recognised as nobles) before year 1400. With "patricians" I refer to those families who from time immemorial were recorded as local and regional leaders, and usually as a base for their power had vast landed properties. With "knight" I refer to warrior class that emerged and developed during 900 - 1300 AD.
The original nobility was comprised of those two categories, patricians and knights. The patricians soon developed into higher nobility, and were often granted land and titles by king or ruler. To administer vast and scattered estates they needed local commanders, who in their turn needed well armed warriors to defend properties. During 11th, 12th and 13th centuries duties and privileges (e.g. to maintain an armed force and enjoy tax exemption) became formalised and hereditary.
Among knights one could originally distinguish two classes: nobiles (who belonged to hereditary and wealthy higher nobility, usually derived from patricians), and milites (the lower nobility which served as officers in castles of higher nobility).
During 12th and 13th centuries these two groups, nobiles and milites, were merged, as milites gained priveleges, built their own castles and married daughters of nobiles.