Classical #Intercolumniation is a complex topic with myriad rules that were developed after lots of experimentation by Greek as well as Roman architects.

The primary purpose of #colonnades or multiple columns was both practical (to support heavy weight) and aesthetic ("imposing effect of high relief" as #Vitruvious wrote in https://www.gutenberg.org/files/20239/20239-h/20239-h.htm#Page_78).

The architects paid keen attention to the thickness of columns as well as the spacing between them. They experimented with "columns close together, … with intercolumniations a little wider, … more open still, … and farther apart than they ought to be," until they settled on column spacing "with the intervals apportioned just right."

With variable spacing came the need for adjusting thickness of shafts which had to be "enlarged in proportion to the increase of the distance between the columns," without which, "the column will look thin and mean, because the width of the intercolumniations is such that the air seems to eat away and diminish the thickness of such shafts." They also wanted to avoid proportions that would make the "shaft look swollen and ungraceful, because the intercolumniations are so close to each other and so narrow." So, it wasn't just the design of an individual column that was parameterized with the single parameter µ, first mentioned in https://pixelfed.social/p/Splines/790357912719769731 and further described in https://pixelfed.social/p/Splines/790417950261292263. Intercolumniation was also codified in terms of column width (effectively parameterized by µ).

Beyond the appearance, there were practical considerations. While walls (which came before columns) were made of bricks, the dominant material for columns and entablatures were stone. As such, regardless of the width of individual columns, the gap could not be increased beyond certain limits, for the spans above the column could break.

Materials such as timber for beams allowed more experimentation.