It is generally agreed, both by its proponents and by its opponents, that the hardest problem facing panpsychism is what has become known as the “combination problem”. This term comes from William Seager (1995), although in the contemporary literature the problem itself is generally traced back to William James ([1890] 1981).[23] The combination problem is most obviously a challenge for constitutive micropsychism, although as we shall see there are forms of it that threaten other kinds of panpsychism. According to constitutive micropsychism, micro-level entities have their own very basic forms of conscious experience, and in brains these micro-level conscious entities somehow come together to constitute human and animal consciousness. The problem is that this is very difficult to make sense of: “little” conscious subjects of experience with their micro-experiences coming together to form a “big” conscious subject with its own experiences.