  While reflection on property dualism or anomalous monism can lead to our next property-based problem, another route is by way of the doctrine of  non-reductive physicalism.  Like the property dualist, the non-reductive physicalist holds that mental properties are not physical.  But unlike the property dualist, the non-reductive physicalist insists on a strong dependence of the mental on the physical: mental properties are “realized” or “constituted” by physical properties. This strong tie between the mental and physical is the subject of a large contemporary literature, some of which we touch on below.