cornerstones

Cornerstone refers to the first stone set in the construction of a masonry foundation, traditionally placed at a corner and aligned to guide the placement of subsequent stones. In many historical buildings, the cornerstone also carried ceremonial significance, often marked with inscriptions or symbols and used during a formal laying ceremony. Depending on local tradition, the cornerstone might incorporate a time capsule or a commemorative message and was sometimes the original reference point for surveying.

The term has acquired a broader metaphorical meaning: something that is essential, fundamental, or foundational to a system, organization, or idea. Phrases such as "the cornerstone of democracy" or "education is the cornerstone of a stable society" exemplify this usage. In architecture, other related terms include the keystone, the buttress, and the capstone, which describe different structural roles in arches and walls.

In contemporary construction, the ceremonial aspect of laying a cornerstone persists in many places, though it is largely symbolic. Modern foundations are engineered for load-bearing performance, while the cornerstone plaque often serves as a historical record. The concept remains widely used in policy and planning discourse to denote core principles, core values, or indispensable elements of a project.