Walking through the central naves of Romanesque basilicas, the visitor is accompanied on the right and left by arcades, the arches of which are supported by either columns or pillars.
Especially in buildings with wooden ceilings, attentive observers will sometimes notice discrepancies. Instead of two rows of identical pillars, pillars and columns alternate on each side, either in a strict rhythm, or two columns can follow one pillar. In the first case, experts speak of a Rhenish, in the second of a (Lower-)Saxon "Stützenwechsel" ("alternation of supports").
St. Godehard Hildesheim, Saxon "Stützenwechsel"
The reasons for these appear to be varied.
Geography might be a primary explanation, yet both the construction of St Cyriacus in Gernrode, built in the late tenth century (an important structure for the period), as well as the twelfth-century Basilica of Sts George and Pancrace in Hecklingen, also in the former territory of the Ottonian Saxons, feature a single, that is Rhenish alternation of supports.
Basilica of Sts. George and Pancrace, Hecklingen
This appears to be logical in case of structures with bound systems. The pillars mark the corners of the bays in the central nave, of which the squares, beginning with the transept square, determine the entire floor plan. The weaker columns between the pillars support the half-sized aisle bays.
Numerology has also been mentioned as a reason: with the Saxon "Stützenwechsel", the total of four pillars may allude to the Evangelists and the twelve columns on Christ's disciples or the tribes of Israel.
Translation: Erik Eising (M.A.)