bases, bases, bedrocks, bottoms, cornerstones, footings, foundations, grounds, groundworks, keystones, roots, underpinnings, warps

anchorages, beds, braces, bulwarks, buttresses, frameworks, infrastructures, mounts, props, shores, stays, substrata, substructures, supportsassumptions, justifications, premises(also premisses), presumptions, presuppositions, rationales, suppositions, theories, theses, warrantsbackbones, centers, cores, cornerstones, eyes, foci(also focuses), hearts, hubs, kernels, keystones, nuclei(also nucleuses), seatsessences, quintessences, souls, touchstones