The phrase "be foundation for" implies that something is the basis or starting point for a concept or idea. Antonyms for this phrase could include words like "disrupt," "undermine," or "weaken." These words imply the opposite effect of being a foundation; disrupting means to interrupt or cause a disturbance, undermining implies weakening the foundation from below, and weakening implies a loss of strength or stability. Other antonyms might include "discard," "ignore," or "neglect," which suggest not giving something the necessary attention or consideration to serve as a foundation. In contrast, finding synonyms for "be foundation for" could include words like "establish," "ground," or "root," which all imply a solid and fundamental starting point.