MassMutual | 133,890 followers on LinkedIn. Living mutual has always been at the core of our human existence, and it's the principle that's guided us since our founding in 1851. It's not a concept we invented, but one we champion for the simple reason that people take it for granted today. While the world would have us strive for independence, the truth is when we depend on one another, we aren't just more secure - life is happier and more fulfilling.