Architects can gain knowledge through trial and error but we don’t need to reinvent what we already know.
The following plans are from different cultures, different periods, and different architects, so their similarity points to common principles. The architect’s imprint vanishes when the designs are right. They become universal, and it is difficult to know which architect did which plan.
Design principles explain architecture. They fit well into three categories:
Spatial Rules - are general principles of organization, circulation, privacy, natural light, enclosure, proportions, and scale. These relationships are true of all activities so they can be factored out of programmatic rules as general spatial rules.
Programmatic Rules - relate to specific activities and their properties. They are plugged into space.
Structural / Economic Rules - determine practical limits like span length, column location, etc.
The distinction between spatial rules and programmatic rules is helpful for making decisions. Because activities share the same important things in common like square footage, ceiling heights, circulation, natural light, etc, they can be factored out as general spatial rules. Specific activities require these things, so they are programmatic, but they also have meaning in their being shared across all activities. They explain the basic human requirements for space. As long as a building is spatially correct, it can generally adapt to whatever use is needed without significant changes.