_First published Thu Feb 3, 2005; substantive revision Tue Jan 31, 2023_Neutral monism is a monistic metaphysics. It holds that ultimate reality is all of one kind. To this extent neutral monism is in agreement with the more familiar versions of monism: idealism and materialism. What distinguishes neutral monism from its monistic rivals is the claim that the intrinsic nature of ultimate reality is neither mental nor material but rather, in some sense, neutral between the two.Neutral monism is compatible with the existence of many neutral entities or kinds. And neutral monism is compatible with the existence of non-neutral entities or kinds—mental and material ones, for example—provided that they are, in some sense, derivative of ultimate reality’s neutral intrinsic nature. Most versions of neutral monism have been pluralist in both these respects. They were conceived as solutions to the mind-body problem. Their goal was to close the apparent chasm between mental and material entities by exhibiting both as grounded in more basic neutral entities.Any version of neutral monism will therefore have to answer the following three questions: (1) What are the neutral entities and what is their nature?, (2) What is the relationship of these neutral entities to matter?, and (3) What is the relationship of these neutral entities to mind?* * *## 1. Neutral Monism### 1.1 NeutralityBoth of the terms that make up the label “neutral monism” are problematical. Because the questions to which the notion of neutrality gives rise are unique to neutral monism, they need to be addressed first. Most versions of neutral monism assume a plurality of basic, neutral entities (these could be substances, events, tropes, universals, etc., depending on the specific form of the view). What does it mean for an entity to be neutral? Here are five proposals: 1. _The Neither View:_ A basic entity is neutral just in case it is intrinsically neither mental nor physical. 2. _The Actual Constituent View:_ A basic entity is neutral just in case it is a constituent of both physical and mental non-basic entities. 3. _The Possible Constituent View:_ A basic entity is neutral just in case it can be a constituent of both physical and mental non-basic entities.