Post Author: Bill Pratt
In previous posts we have surveyed the physicalist and dualist positions with regard to human beings. Now it is time to start looking at arguments for the dualist position. Before we start to defend dualism, we need to introduce the concept of identity, which will be an extremely important concept in the debate.
The law of identity simply states that A is A. Yes, it’s that simple, but we need to draw out some implications from this law. Philosopher J. P. Moreland helps us understand with the following example:
Suppose you want to know whether J. P. Moreland is Eileen Speik’s youngest son. If J. P. Moreland is identical to Eileen Speik’s youngest son (everything true of one is true of the other), then in reality we are talking about one single thing – J. P. Moreland, who is Eileen Speik’s youngest son. However, if even one small thing is true of J. P. Moreland and not true of Eileen Speik’s youngest son, then these are two entirely different people. Furthermore, J. P. Moreland is identical to himself and not different from himself. So, if J. P. Moreland is not identical to Eileen Speik’s youngest son, then in reality we must be talking about two things, not one.
Where does this example take us? Moreland explains:
This illustration suggests a truth about the nature of identity known as Leibniz’s Law of the Indiscernibility of Identicals: For any entities x and y, if x and y are identical (they are really the same thing – there is only one thing you are talking about, not two), then any truth that applies to x will apply to y as well. This suggests a test for identity: If you could find one thing true of x not true of y, or vice versa, then x cannot be identical to (be the same thing as) y. Further, if you could find one thing that could possibly be true of x and not y (or vice versa), even if it isn’t actually true, then x cannot be identical to y.
Hopefully you have followed along, because now Moreland explains why this matters to the mind/body debate:
Physicalists are committed to the claim that alleged mental entities are really identical to physical entities, such as brain states, properties of the brain, overt bodily behavior, and dispositions to behave (for example, pain is just the tendency to shout “Ouch!” when stuck by a pin, instead of pain being a certain mental feel). If physicalism is true, then everything true of the brain (and its properties, states, and dispositions) is true of the mind (and its properties, states, and dispositions) and vice versa. If we can find one thing true, or even possibly true of the mind and not of the brain, or vice versa, then dualism is established. The mind is not the brain.
At this point, it is critical to note that it is not enough for the physicalist to show that mental and physical entities in the human brain/mind are in a causal relation or are constantly conjoined.
It may be that brain events cause mental events or vice versa: Having certain electrical activity in the brain may cause me to experience a pain; having an intention to raise my arm may cause bodily events. It may be that for every mental activity, a neurophysiologist can find a physical activity in the brain with which it is correlated. But just because A causes B (or vice versa), or just because A and B are constantly correlated with each other, that does not mean that A is identical to B.
Therefore, and this is critical, physicalism cannot be established on the basis that mental states and brain states are causally related or constantly conjoined with each other in an embodied person. Physicalism needs identity to make its case, and if something is true, or possibly true of a mental substance, property, or event that is not true or possibly true of a physical substance, property, or event, then physicalism is false.
In future posts, we will look at whether mental states and brain states are truly identical. Stay tuned!!