There is another way to deal with the problem of causation, commonly known as dual aspect theory originally espoused by the 17th century philosopher Spinoza. It ascertains that mind and matter are both manifest aspects of a more fundamental property of the nature, which appear to interact by virtue of some unfolding, grounding process within nature itself. So, the experiential aspect is inseparable from its physical correlate, but neither of them can be analysed in terms of the other. There have been recent proponents of this view. For example, physicist Pauli writes:
It would be most satisfactory of all if physis and psyche (i.e., matter and mind) could be seen as complementary aspects of the same reality. (Jung and Pauli, 1955, p.210)
A consequence of this perspective is that everything, including objects such as a stone or stick, has both a mental and a physical aspect. A modern version of this view is developed by Charlmers, who claims that the fundamental feature behind mind and matter is information. Some objections to this view can be raised too.
- Dual-aspect theory seems more an attempt to avoid the problem than to solve it. The issue of how such apparently different phenomena could be aspects of one thing remains obscure. Let us consider information, as Charmers proposes. The fundamental problem here is that an event becomes information only if it is cognised. An ability to experience must be already present for anything to be information. Therefore, either the experience is prior to information, or information, experience and its physical correlate appear at the same time. In the former case information cannot be a fundamental feature, while the latter endorses panpsychism (as argued by Whitehead and more recently Seager). This view would allow even a thermostat (as Chalmers tentatively suggests) to have, albeit a very primitive, experience. But this is incohesive. Inanimate objects can be fully explained by physical principles, so granting them another fundamental feature seems unnecessary. The behaviour of a thermostat can be satisfactorily accounted for without it having experience. The metal in a thermostat expands because of its intrinsic qualities and the laws of physics, not because it receives (feels) the information that the temperature has changed. Becoming aware and acting upon information is a very different matter from an automatic reaction, and this distinction is not only blurred, but difficult to explain from this position.
- As with some other already mentioned models, dual aspect theory is also unable to adequately explain certain discrepancies between neural events and its phenomenal correlates (e.g. antedating that will be discussed below).