Rather than adopt a position of monism or dualism when it comes to properties, D.H. Mellor adopts what he calls a ‘pluralist’ approach to properties.
It would be strange that in this huge universe of ours, and amongst its infinite properties or objects, that there were only two kinds of entities – mental and physical. Indeed I would more likely go for one kind of entity or property rather than the rather-too-neat postulation of two. Or, as with Hugh Mellor, go for a plurality of properties or objects.
This multiplicity or plurality of kinds of objects or properties seems to go against the scientific search for simplicity and the metaphysical desire for ontological parsimony. However, we can't reject the possibility of a plurality of different properties simply because it will complexify our scientific and philosophical endeavours. Perhaps the world simply is complex and it's complex because it's made up of a plurality of different objects or properties.
Of course scientists will happily accept the fact that there “is a great plurality of properties” (109). It's just what we conclude from this scientific acceptance of a prima facie plurality.
For instance, does this mean that a distinct property can't be reduced to another distinct property? Are these properties basically irreducible? If they aren't, then are they genuinely distinct at all?
Take Mellor’s own list of properties: electrical, gravitational, chemical, biological, psychological. Many philosophers will argue that the psychological is indeed reducible to the biological; though also to the chemical, electrical and even the gravitational.
The biological is essentially made up of the chemical; though it isn't strictly reducible to the chemical (for many reasons). Perhaps the chemical can be (fully?) reduced to the electrical and even the gravitational.
Mellor himself says that “there is no fundamental distinction of kind amongst them” (109). Rather, there “are lots of little distinctions, and interesting questions about which are reducible to which” (109). What Mellor is saying here doesn't make what he says any different to what the average scientist says and not even to the scientific reductionist. So how does this play on his ontological ‘pluralism’ at all?
Scientists are reductionists who also accept that “there is no fundamental distinction of kind amongst them” (109). They will also say that there are (only) “lots of little distinctions” to be made about them. Mellor even accepts reduction when it comes to (some of) these properties. What does his ontological pluralism amount to and how is it different to ontological monism and ontological dualism?
Mellor accepts that it may be possible to reduce “a lot of sciences... in some non-trivial sense to one basic science” (109); though he also says that this is “not a very fundamental one” (109). He then stresses what it is that all the sciences share and how it is they differ.
For a start, all the natural sciences “are involved with phenomena” (109). These phenomena “can be physical, chemical, biological, psychological, or whatever” (109). Not only that: these different phenomena “are all studied in ways that are methodologically similar” (109). However, all these disciplines will “differ in detail according to their subject-matter” (109). So if there are differences, these differences will be brought about by the different subject-matters of the natural sciences. Despite that, their methodologies will be 'similar' regardless of the differences ‘in detail’. As in the case of Mellor’s ontological pluralism, he says little that is controversial or even interesting here.
D.H. Mellor or Parapsychology
Hugh Mellor offers a very interesting criticism of parapsychology. It's similar to Karl Popper’s view that ‘pseudo-sciences’ - such as Freudianism and Marxism - make it the case that they can't be falsified. Parapsychology goes a step further than this. Its failure to prove something counts “as a kind of success” (110). Mellor writes:
“What’s wrong with parapsychologists is that they count failure as a kind of success; that is, they think that failure to understand a phenomenon bestows a kind of glamour upon it, makes it something special, a paraphenomenon. It does nothing of the sort: all it means is that there’s something we still don’t understand.” (110)
Of course this “failure to understand a phenomenon” - and the concomitant bestowing of “a kind of glamour upon it” - is something that can be applied to what people believe about UFOs, extra-terrestrials, astral travelling, ley lines, ‘the stars’ and all the rest. One gets the feeling that a lot of true believers in this stuff wouldn't even like their darling subjects to be proved by science – that would take away the glamour and the mystique (which is at the heart of all these subjects and pursuits).
Of course it's also the case that, as with Marxism and Freudianism, claims about UFOs, extra-terrestrials, astrology, and the like are also unfalsifiable in principle because the believers in such stuff always rely on some ‘auxiliary hypothesis’ to counteract any evidence that works against what it is they believe. (For example, non-believers never see UFOs because they are brainwashed by the CIA or extra-terrestrials keep well away from all sceptics.)