In this essay I shall attempt to show that you cannot know what it is like to taste Marmite unless you have tasted it, even if you knew everything physical that happened to a person when they taste Marmite according to modern day physics. I will then discuss the implications of this as to whether the mind is physical.

To begin with, I shall explain what I mean by knowledge. In this case I shall be using Descarte’s condition that if something is clearly and distinctly perceived, we can say to have knowledge of it. I shall however be going further by assuming that there is also an external world. This seems to me to be clearly and distinctly perceived, and is also verifiable by other people. Therefore we can claim to be able to know everything physical about what happens to a person when they taste something. We could observe all their bodily functions, specifically, the molecules of Marmite causing taste buds on the tongue to send messages to the brain via the nervous system, and certain fibres in the brain firing. We would be able to observe this with our own eyes and through the use of various medical apparatus, and would also be available for other people to observe and report the same observation. We may not know the true underlying nature of the observed, but would have knowledge of the sense data caused by these physical processes.

However, surely this would not be knowledge of what Marmite actually tastes like. By observing the physical processes occurring in the body we may be aware of the various patterns of electrical current interacting in the nervous system and brain, but not of the experience or “qualia” which a person has when they taste Marmite. This is because these qualia are only experienced by the person doing the tasting. To make this clearer I have devised an argument to show that the opposite is false.

Premise 1: All physical processes of a body are publicly observable

Premise 2: Person A observes all physical processes of person B who is tasting Marmite

Conclusion 1: Person A has Knowledge of all physical processes occurring in Person B’s body whilst tasting Marmite

Conclusion 2: Person A has knowledge of qualia experienced by person B.

For this argument to be valid there would have to be another premise in between the first and second conclusion. This would be that knowledge of all physical processes occurring in person B whilst tasting Marmite is also knowledge of the taste or qualia of Marmite. However it seems clear to me that this premise is not true. Never in my experience have I observed someone eating Marmite and thereby experienced the taste qualities myself. Admittedly I have not observed the nerves in the tongue sending nerve impulses to the brain and the brain thereby reacting, but I am aware that neuroscientists have done so and not managed to experience another persons qualia. It seems therefore that the only way we can know what it is like to taste Marmite is to taste it ourselves.

There are however some branches of philosophy which take a different view on this which I shall now describe and then attempt to dispute. Radical behaviourism which was adopted by Watson and Skinner in the early 20th century states that all mental states do not exist and are simply acts of behaviour or dispositions to behave thereby denying the existence of qualia. For example a person who might traditionally be described as being in pain due to being shot in the foot might in behaviourist terms be described as jumping around, crying and being disposed to shouting and cursing. However from my own experience which I clearly and distinctly perceive I know that when I cut my finger I not only curse and shout but also have an inner experience. Although this cannot be identically conveyed to another person, it can be represented through words which other people may similarly report. For example this inner experience is uncomfortable and feels like a stabbing sensation in my foot.

Other people who have had a similar experience will be able to report similar experiences. As well as clearly and distinctly perceiving this sensation I can also see a function which this pain causes in my body, in that it brings ones attention to whatever has caused this damage so that one may remove oneself from the situation to escape further damage. If God has created man so as to be a well designed being we can infer from the other functional roles in our body that this was intentional. Or if God has not created us and we are simply a product of evolution, the pain still serves as the same function. If something has a function and is subjectively experienced by apparently most people, although not provable by traditional empirical methods, it seems more likely that these qualia do exist.

To further illustrate the absurdity of this doctrine we can observe this rather amusing piece of dialogue between two radical behaviourist lovers after they have fornicated.

Male: That was great for you! But how was it for me?

Female: O I am so pleased, it was great for you too.

It seems clear that this couple would have difficulty living their lives, and that this doctrine is counter intuitive.

There is another reductionist theory called type-identity theory which states that mental states are identical with brain states. Therefore the mental state of pain would be identical with c-fibres firing in the brain. The identity theorists use an analogy of lightning being the motion of electrical charges, whereby the lighting represents the mental states and the electrical charges the brain states. However the physical features of brain states do not convey any understanding of the phenomenal features of qualia. The analogy is also rather week as both the electrical charges and the lightning are publicly verifiable to anyone who observes these. It is possible to imagine another world, exactly like our own except that beings have no conscious mental life whatsoever. The question may then be asked as to what those beings lack. As it is not anything physical this suggests that physicalism is false.

It is therefore possible that the mental is of an entirely different nature or substance. It is argued by dualists that the mental has different properties to the physical. Physical substance has extension in space, is divisible and observable by anyone. The mental however does not have extension is space, is indivisible and only observable through introspection. There is however the problem of how something mental can interact with something physical if they are of a completely different nature. Interaction indisputably takes place between qualia and the physical. If for example someone was slapped in the face, the nerve endings would send nerve impulses to the brain which would cause c-fibres to fire. This person would then feel the sensation of pain. Depending on the intensity of this pain, the person might decide to slap the other person back. This example shows that the reaction of the person being slapped would be affected by his qualia or mental states.

Parallelism and occasionalism attempt to explain the interaction between the mental and physical by using God. Parallelism states that God synchronised the mental and physical at the beginning of time so that the mental state of pain would happen simultaneously as c-fibres firing in the brain. Occasionalism states that every time a certain brain state occurs, God intervenes and causes a certain mental state to arise. Both of these arguments require an argument for the existence of God. Secondly, parallelism would imply that we have no free will and occasionally would suggest that God was very busy, having to deal with everyone’s mental states all the time.

Idealism is another form of monism which reduces everything to the mental. As the only experience we have of a seemingly physical world is mental states caused by sense data which we have no reason to believe are identical with the true nature of the physical, how can we be sure that anything other than the mental exists? Or put another way, as we have no direct clear and distinct perception or experience of the physical we have no basis for forming an a-posteriori belief that it exists. This following argument is based on a combination of Descartes’ and Hume’s conditions for knowledge.

Premise 1: All our knowledge comes from experience

Premise2: We have no clear and distinct experience of the physical

Conclusion: The physical world does not exist.

In my opinion the mental and the physical are two aspects of the same underlying nature. This theory is also known as property dualism. If for example we were to demonstrate a remote control car to a person 100 years ago they would probably conclude that there was some supernatural force acting upon it. Now however due to progress in science we know that this is simply caused by certain waves which are not visible to the naked eye. It may be that these qualia or mental states are of a similar nature but that we have not yet developed the technology to observe them as we might say infra-red.

Advancements in modern physics have shown that what we see as matter does not actually consist of a substance which takes up space and time in the conventional sense. At the microscopic level this “matter” has a tendency to exist at certain times or probability waves which are in a state of constant flux. This is rather hard for our minds to understand as we are so used to viewing the macroscopic world as having defined substances in a specific place at a specific time. It seems therefore likely that the “mental” and “physical” share this underlying nature, although this will not be able to be proven until our science is sufficiently advanced.