Consider a possible world in which the fundamental constituents of reality are mental in nature. Suppose a kind of mental atomism holds: there are basic elements that combine to form less basic elements. We thus have simple and complex mental entities. But suppose further that there is a special kind of emergence in this world whereby entities we would describe as physical emerge from mental elements. That is, ordinary physical objects, solid and extended in space, emerge from mental entities. This would pose a problem for the philosophers in this world: how is such a thing possible? Some may deny emergence, insisting that the physical entities have another origin altogether—maybe created by a deity enamored of all things physical. Others may declare the physical things to be illusory and offer to eliminate all talk of them. And there may be those who defend a reductionist view of the physical entities: they reduce to mental entities and their properties. Certainly the apparent emergence poses a theoretical challenge, because it seems impossible to understand how the physical could emerge from the mental. A few philosophers respond with a startling hypothesis: the emergence is possible because the underlying mental entities possess a hidden physical aspect, and this is what enables observable physical entities to come into being. They call this doctrine “pan-physicalism”—the doctrine that the mental entities of this world harbor a physical dimension. Evidently, it is a doctrine with the same general shape as pan-psychism, except inverted, and motivated in much the same way. Pan-psychism explains the emergence of mind from matter by crediting matter with mental properties, while pan-physicalism explains the emergence of matter from mind (in the possible world described) by crediting mind with physical properties.
In the actual world there is no such emergence: physical things don’t emerge from combinations of mental things. There is no way to combine thoughts and sensations in such a way as to produce a table—you have to use atoms and molecules. So there is no argument for pan-physicalism based on the emergence of the physical from the mental in our world. But that doesn’t mean there might not be other arguments to the same conclusion, and indeed such arguments have been given. For instance, it has been held that the causal powers of mental states and events require that they have a physical aspect: the only way mental things can cause physical things is by the mental things having a physical nature. Thus we get different varieties of identity theory. The general thought is that the mind can only influence the body if it is not disconnected from the body—that is, if it has a physical nature too. That is the only way to capture the proximity required by causation: mental events can only exist in a causal sequence in space if they have a physical nature. Without this embedding in the physical world mental events would be deprived of causal efficacy. Such arguments lead to a pan-physicalist position: all mental events partake of the physical in some way—they have a physical aspect. It is not that they exist in a realm removed from that of the physical—that would preclude psychophysical interaction.
It is possible to combine pan-physicalism with pan-psychism. Everything mental has a physical aspect and everything physical has a mental aspect. Pan-physicalism explains mental causation and pan-psychism explains mental emergence. The two are logically compatible and each offers explanatory benefits. To be sure, neither doctrine is observably true—they are speculative hypotheses—but perhaps in some possible world they are part of perception-based common sense. In this world ordinary perception of physical reality reveals its mental aspect, while introspection reveals the physical dimension of the mind. Here the metaphysics will look very different to the inhabitants: there is no radical separation of the mental and the physical, though a division of aspects is accepted as common sense. The mind is experienced as partly physical and the world is experienced as partly mental. Mental causation is not a mystery and neither is the emergence of mind from matter. Everything is seen to have a dual nature; nothing is homogeneous through and through. Physics deals in mental properties as well as physical properties, and psychology is thoroughly psychophysical. No one is a materialist and no one is an idealist. Reality is regarded as always and inherently a mixture.
My purpose in describing this world is to make the metaphysical position in question visible. We are familiar with pan-psychist metaphysics and with pan-physicalist metaphysics, reflecting the old dualisms and monisms; but no one (that I know of) ever talks about a view that combines both, and which has no established label. This is the idea that reality is an inextricable combination of two strands with neither having priority. It may not seem to us that this is so, given our epistemic predicament, but it could be the objective truth. Everything is mental and physical. If we like, we can relax the doctrine a bit by speaking of proto-mental and proto-physical properties, so as to avoid the assumption that the physical nature of the mind is captured in our current physical paradigms and that the mental nature of matter reflects the way existing minds are formed. Maybe the underlying properties are at some remove from current conceptions of the mental and the physical, though still recognizably distinct from each other. There is a fundamental dualism of aspects but the aspects are ubiquitous and intertwined: no mind without matter and no matter without mind—though the words “mind” and “matter” are freed from their current limitations. What we know is that there is something about physical things that allows minds to arise from them, and something about minds that allows them to interact with matter, but we are hazy about the details. We know there are two types of property at work, but we are only partially cognizant of the difference. The basic metaphysical picture is unaffected by this ignorance, namely that everything is partly physical and partly mental. As I say, my purpose is to make this position visible, not to endorse it—though I think it has an attractive shape. It is simply the conjunction of pan-psychism and pan-physicalism (we might call it “pan-double aspect-ism”, or simply “pan-ism”). Nothing is either one thing or the other; everything is a bit of both.
 I will make free use of the words “mental” and “physical” here, fully aware of their lack of proper definition. To fix ideas, we can understand the physical as what is spatially extended and the mental as consciousness (however that is to be understood). I won’t discuss this difficult subject further.
 Spinoza maybe.
 Is it ever possible fully to endorse a metaphysical position on this scale? Doesn’t intellectual honesty require extreme caution? Of course, one can like a certain position very much.