<prompt> Human: I am currently contributing about 20 between my contributions and my employer of my yearly salary into my Vanguard 401K target retirement date account that is 90 stocks. As a young, single person why shouldnt I be putting all of that in an index fund?  <response>: If you dont want to have any bonds in your portfolio and are comfortable with taking on that much more risk then nobody should convince you otherwise. Common reasons for owning bonds include having a source of dry powder to rebalance from in bear markets, reducing volatility, and providing a steady source of return.Be very careful about assuming you are comfortable seeing the value of your portfolio halve in a severe bear market. Until youve experienced one it may be better to err on the side of caution. 