Cartesian dualism leads to a problem associated with the connectivity problem we have just discussed: if reality consists of two different "substances", then what connects these substances in one unified "reality"? What is the medium which sustains their respective existences and the putative difference relationship between them? One possible (wrong) answer is that their relationship is merely abstract, and therefore irrelevant to material reality and devoid of material influence; another is that like the physical epiphenomenon of mind itself, it is essentially physical. But these positions, which are seen in association with a slew of related philosophical doctrines including physicalism, materialism, naturalism, objectivism, epiphenomenalism and eliminativism, merely beg the question that Cartesian dualism was intended to answer, namely the problem of mental causation.
Conveniently, modern logic affords a new level of analytical precision with respect to the Cartesian and Kantian dichotomies. Specifically, the branch of logic called model theory distinguishes theories from their universes, and considers the intervening semantic and interpretative mappings. Calling a theory an object language and its universe of discourse an object universe, it combines them in a metaobject domain consisting of the correspondences among their respective components and systems of components, and calls the theory or language in which this metaobject domain is analyzed a metalanguage. In like manner, the relationship between the metalanguage and the metaobject domain can be analyzed in a higher- level metalanguage, and so on. Because this situation can be recursively extended, level by level and metalanguage by metalanguage, in such a way that languages and their universes are conflated to an arbitrary degree, reality can with unlimited precision be characterized as a "metalinguistic metaobject".
In this setting, the philosophical dichotomies in question take on a distinctly mathematical hue. Because theories are abstract, subjectively-formed mental constructs, the mental, subjective side of reality can now be associated with the object language and metalanguage(s), while the physical, objective side of reality can be associated with the object universe and metauniverse(s), i.e. the metaobject domain(s). It takes very little effort to see that the mental/subjective and physical/objective sides of reality are now combined in the metaobjects, and that Cartesian and Kantian "substance dualism" have now been transformed to "property dualism" or dual-aspect monism. That is, we are now talking, in mathematically precise terms, about a "universal substance" of which mind and matter, the abstract and the concrete, the cognitive-perceptual and the physical, are mere properties or aspects.
- In the conventional model, percepts are objective observables that actively imprint themselves on, and thereby shape and determine, the passive mind and its internal processes. But a more general (and therefore more scientific, less tautological) description of percepts portrays them also as having a subjective perceptual aspect that is identified, at a high level of generality, with the Creation Event itself. This is just an extension of Wheeler's Observer Participation thesis ("only intelligent entities are observers") to physical reality in general ("everything is an observer", with the caveat that it's still possible, and indeed necessary, to reserve a special place for intelligence in the scheme of things).
- The surprising part, in my opinion, is this. This reduction of all reality to simultaneously active and passive "infocognition" amounts to defining reality as did Hume...as pure experience ("infocognition" is just a technical synonym of "experience" that opens the concept up to analysis from the dual standpoints of information theory and cognition or computation theory). Thus, the Kantian mind-matter distinction, as embodied in the term "infocognition", is simply distributed over Hume's experiential reality by synonymy, bringing the metaphysics of Hume and Kant into perfect coincidence.