What is Dualism and Materialism in the World of Philosophy?

Dualism Vs. Materialism in Philosophy
Studying the brain is one thing, but studying the mind is very complicated! Wondering what's the difference between brain and mind? Well, there are a few differences and philosophies to back the theory of mind being more than just a brain! We discuss two of them - dualism and materialism, and try to understand them in detail.
Definitions in Short
Dualism: Mind and body are separate. Mind is a non-physical thing. It may exist even after the body dies.
Materialism: Mind is a part of the body. It is physical. It dies with the body.
Do you find it interesting to think how you can think? What I mean to say is, where does the power to 'think' come from? Likewise, how do emotions get evoked? How do our 5 senses work? How do you know what's right and what's wrong? What helps you decide? Where do feelings that we call intuitions, come from? You sense danger sometimes, how does that happen? Is all of this just the work of a physically made up brain full of matter, or is there something called consciousness?

All the mental abilities like thinking, perceiving, understanding, relating, deciding come from the mind. So, what is this mind? Is it just the brain? Or is it the brain plus the soul? Let us find some answers from the differences between the two philosophies - dualism and materialism.
Dualism
Dualism states that there is a soul, a consciousness, a spirit inside our body. This consciousness we have is what controls our body through the brain. It is like a frequency that cannot be seen, or is present in the form of matter, but comes out as sound from the radio. The way it directs its path through a radio, the same way, our consciousness directs its path through the brain. Our bodies are like containers of our souls. They carry them till they can, and when they wither off, souls do not die with them, but become individual non-physical entities again.

We need to go back to around 380 BCE, and take Plato's view on soul, from his book 'The Republic'. According to him, the soul has 3 kinds of function:

Growth, nutrition
Motion, perception
Intellect

All the living things have souls which, according to their functions, define them. Known as the degrees of soul, they go like this:

Nutritive soul (plants)
Sensitive soul (all animals)
Rational soul (human beings)

The lowest degree of soul is the nutritive soul which all plants, animals, and humans have. The next level is the sensitive soul, that which can feel and move and perceive, which only animals and humans have. The highest degree, that of intellect, only humans have. In this way, the living being with the higher degree of soul will also possess all the lower degrees.
Plato, the great Greek philosopher, believed that soul is independent of the body. After the body dies, the soul migrates to another physical body.
Soul
Soul leaving the dead body
However, Aristotle disagreed with Plato's belief. According to Aristotle, the soul exists, and so do the 3 different degrees of it, but it is not separate from the body. It withers off with the body, and there is no existence of it outside the body.

In the 17th century, René Descartes, came up with a philosophy that mind is immaterial. He meant that it is non-physical, and has a consciousness and self-awareness that distinguished it from the physical brain. Dualism closely relates to this philosophy.
Problems With Dualism
The difference in the nature of minds
The mind has mainly two properties―subjectivity and intentionality.
Subjectivity: The property of the mind to understand things through personal experiences and observations, and not through an external source.
Intentionality: The quality of mental states―fear, desire, thoughts, beliefs, and hopes.
Example
There is an object―a flower―you can see it, and everybody else can see it. What you are seeing is the sensory perception, that makes an image in your mind. It is the same for all others who are seeing it. Thus, what you are experiencing is shared with others too. This is subjectivity.

What you are making of it, as in, what your thoughts on it are, is definitely going to be different than others'. Your thoughts cannot be shared with others unless you choose to share them. This is intentionality.

The 'problem of other minds' arises here. Because it's different for different people. Physical things have the property of causal relations (the relation between two events―first being the cause, second the effect) with other physical things. With mind, there is this extra mysterious property, along with causal relations, which is not accessible to other minds―intentionality. So, we can completely verify and understand only the mind of self. How do we solve this problem of other minds? If we consider mental states behaviorally, functionally, or physiologically, we can then generalize them to our personal experiences towards instances, according to our behavior, functions, and physiology.
The unity of mind and body
The question that was and still stands is this: how can consciousness―a non-physical thing―affect a physical body, and vice-versa? The interaction between the two needs a medium through which they can communicate among themselves. One answer that was rejected was the pineal gland that exists in the brain. The function of this tiny part of the brain is not known, and so it is said that this gland is used to interact with the non-physical entities outside the body. The reason why this answer was rejected was again the same question, how can a non-physical entity interact with a physical part of the body, the pineal gland being a physical part of the brain.
Types of Dualism
Types of Dualism
This is a type of dualism, which states that there exist two kinds of substance―physical (body) and non-physical (mind). Mind is dependent on the body, cannot stay outside it. Body is only a physical vehicle. It cannot think without the mind. When body dies, mind dies with it.
Property Dualism
This type of dualism states that there is only one kind of substance in the world, which is physical. But it has two kinds of property―physical (body) and non-physical (mind). When physical things are arranged in the proper manner (that of the living beings), they elicit their property of non-physical things. This means that mind is the result of proper structuring of the brain and other physical structures in the body. This is how we feel emotions, pain, and other stuff.
Predicate Dualism
It states that the predicates (declared qualities/attributes) that are used to describe the mental properties like emotions, pain, belief, desires, etc., cannot be re-described as physical properties, even though everything is derived from a physical substance.
Materialism
Materialism states that, everything that exists is physical. Here, there is no concept of a non-physical entity residing in the body. The mind is only the brain. So the body acts according to the functions of the brain. When the body is destroyed, so is the mind with it. The complete existence of that person/body/mind is dead with the physical body. According to materialism, all the mental phenomena, and what we call consciousness, are the result of physical interactions.

Physicalism is the philosophy which is derived from materialism. The prior assumption for materialism was that everything was made of matter (hence, the name), but now there are more acceptable assumptions in physicalism, which answers the questions of gravitational fields, curves in space-time, physical energies and forces, etc., which are definitely not matter. So, mind is the product of matter, which is acting upon matter. For physicalists, matter is primary, mind or soul is secondary, which is in contrast to what idealists believe in. For them, soul is primary, matter is secondary.

Today, a majority of twentieth-century philosophers and thinkers have widely accepted materialism and are of the view that materialism, put broadly, affirms that all phenomena are physical, and there is no reality other than matter moving in space. If all matter were to be removed from the world, nothing would remain--no minds, no illusions, no realities.
If mind was just the brain, could it do all that the mind does? What we think, cannot be known by other people. They need to ask us what we are thinking if they want to know. So, the conclusion is that, both dualists, and the materialists agree on the fact that mind is present. Just that dualists believe in an eternal, spiritual soul that exists in the body, while materialists believe in the physical body itself.