Bootstrapping is a suspicious form of reasoning that verifies a source's reliability by checking the source against itself. Theories that endorse such reasoning face the bootstrapping problem. This article considers which theories face the problem and surveys potential solutions. The initial focus is on theories like reliabilism and dogmatism, which allow one to gain knowledge from a source without knowing that it is reliable. But the discussion quickly turns to a more general version of the problem that does not depend on this allowance. Five potential solutions to the general problem are evaluated, and some implications for the literature on peer disagreement are considered.