US dollar is created by debt and backed by the promise to create more debt. Cash is deemed "safe" because it has the tendency not to fluctate as much as other "investments"-- but only in the short run. TIPs are a bargain with Uncle Satin (er Sam) that Unc will pay a floating rate of return that is determined by Unc. So as long as our big "friend" honors his pledges and you believe the CPI nonsense, your TIPs you buy from the sweet fellow will not lose value as reported by the fearless press and determined by our "friend."
An investor in TIP, the fund does not have this exact guarantee, because any period of deflation may cause real interest rates to spike and drag down TIP valuation--possibly for years, lower than the investor paid to get in. This of course has not happened since the early 1930s and is NEVER expected to happen with Benron at the Fed. We all know he is immortal!!