 Neutral monism is compatible with the existence of many neutral entities. And neutral monism is compatible with the existence of non-neutral entities—mental and material entities, for example—assuming that these non-neutral entities are, in some sense, derivative of the ultimate neutral entities. Most versions of neutral monism have been pluralist in both these respects. They were conceived as solutions to the mind-body problem. The goal was to close the apparent chasm between mental and physical entities by exhibiting both as consisting of groups of the more basic neutral entities.