Some dispositions have causal bases or grounding properties. However, ungrounded dispositions do not have causal bases. Ungrounded dispositions are also known as powers, baseless dispositions, and bare dispositions. Ungrounded dispositions are not supplanted by mechanistic explanations, for even mechanistic explanations ultimately reference dispositions. While some argue that citing dispositions does not really explain anything, dispositions can in fact figure in adequate explanations. Furthermore, scientific explanations reference dispositions with no known grounds. This lends some support for the view that ungrounded dispositions are metaphysically possible. Philosophical arguments based on multiple realizability or the demand for truth-makers fail to show that ungrounded dispositions are impossible.