When considering the meaning of "buy into," some synonyms come to mind that can convey similar ideas. One such phrase is "believe in," which suggests investing hope, faith, or confidence in something or someone. Another alternative is "endorse" or "support," implying a willingness to stand behind or promote an idea, product, or service. "Embrace" conveys a sense of accepting an idea or philosophy wholeheartedly, while "adopt" implies taking on a belief or practice as one's own. Finally, "commit to" or "subscribe to" suggests a level of dedication or agreement that goes beyond simply accepting an idea or product.