Inside the Universes

'cornerstone'

[basis.n.02] as in: the fundamental assumptions from which something is begun or developed or calculated or explained

Examples:
the whole argument rested on a basis of conjecture

'cornerstone'

[cornerstone.n.02] as in: a stone in the exterior of a large and important building; usually carved with a date and laid with appropriate ceremonies

'cornerstone'

[cornerstone.n.03] as in: a stone at the outer corner of two intersecting masonry walls