1. Metaphysics

2. Metaphysics is the study of the basic structures of reality:
Being and nothingness
Time and eternity
Freedom and determination
Mind and body
Thinghood and personhood
Space and time
Supreme being(s) and nature
Metaphysics is sometimes referred to as “first philosophy” because it examines questions that lie at the heart of many other areas of philosophy.
For example, “Do people have rights?” is a question from social/political philosophy.
A metaphysician would say that in order to answer this question, we must first ask, “What is a person?”

3. The Philosopher’s Approach to Metaphysics
As you know, philosophers begin by asking questions:
What, ultimately, is reality?
This question can lead to many other considerations:
What are the basic constituents (building blocks) of reality?
How many basic building blocks are there? One or many?
What are these building blocks made of?
Are they material or mental, or made of neither?
From here metaphysical philosophers ask related questions:
What is matter? What is mind?
What is it to exist? What is “being”?
Why is there something and not nothing?

4. Are scientists best qualified to answer questions about reality?
Theories of quantum physics say that reality is composed of subatomic particles:
Atoms
Electrons
Protons
Quarks
In strictly scientific terms, the chair you sit on is really a cloud of subatomic particles held together by an electromagnetic field. The same can be said of you, too.
There is no doubt that science helps us explain much of the world in which we live, whether it be biology, physics, chemistry, ecology, etc.

5. Metaphysicians might argue, however, that the answers to some of the greater questions about reality and being do not lie in science:
Scientific theories come and go with time. Some theories developed even as recently as the early 1900s are now seen as out of date. Today’s theories may be viewed similarly in the future.
Metaphysicians try to supply answers to questions about reality that are general rather than specific and durable enough to stand the test of time. For this reason, philosophers tend to use reasoning or rational arguments rather than sensory experience to explain reality.
Common-sense realism is a non-philosophical theory about reality. Common-sense realists believe that reality consists only of objects that can be viewed through the senses (e.g.: cell phone, soccer ball, guitar, etc.).
Many philosophers view common-sense realism as lacking true exploration of truth.

6. Prominent Metaphysical Theories
Idealism
Metaphysical idealism is theory of ontology (dealing with reality and the nature of being) that holds that reality itself is incorporeal (has no physical form) at its core. Idealists believe that reality consists of ideas and the minds that house them.
George Berkeley ( CE) was an Irish philosopher and bishop, who was also an idealist. He said that material things have no real existence and that true reality exists in the mental realm.
Berkeley held the belief that what people “common-sensically” view as material objects are actually bundles of ideas that God placed in the minds of humans. He called this theory immaterialism. Today it is also called subjective idealism.

7. Realism
Plato ( BCE) developed the theory of realism, which suggests that reality consists of ideal forms, or ideas, that are timeless, unchanging, immaterial, and more perfect than things in the material world.
Plato wrote a series of dialogues structured as conversations between philosophers on a variety of subjects. In these writings, he has Socrates reveal his Theory of Forms:
The material world as it seems to us is not the real world, but only an "image" or "copy" of the real world.
The forms are abstract representations of the many types of things and properties we feel and see around us, that can only be perceived by reason.
There are, then, two worlds: the apparent world (what can be experienced through the senses), which is constantly changing, and the world of ideal forms (unseen, unchanging, and immaterial).

8. Materialism
The Pre-Socratic philosophers first proposed the theory that everything that exists has a physical form and is composed of matter. This theory is called materialism, or sometimes physicalism.
Materialists refer to matter as minute particles in motion and forces such as gravity. Even people’s thoughts, consciousness, and memories are thought to be made of matter.
Thomas Hobbes (1588–1679 CE) was an English philosopher, who supported materialism as a theory of reality, though this was not popular at the time.
In The Leviathan, he says ideas like the human soul must have a physical form in order for us to perceive them. In this way he tries to explain the essence of a thing (what makes a thing what it is).
“The human soul, separated from man, subsists by itself.”

9. Monism
Some metaphysicians believe that reality is made up of one all-encompassing thing. This theory is called monism (from mono meaning “one”). Thales of Miletus was a Pre-Socratic monist.
Even though objects in the physical world appear to be different from each other, monists believe they are all made up of the same basic building block, or substance. This building block can be material or mental.
Baruch Spinoza ( CE), a Jewish-Dutch philosopher, theorized that all reality was made up of the same divine substance, in other words God.
If God, as a supreme being, is infinite and without end in time and space (as was commonly believed), then all things must be contained within (or be a part of) God. Therefore, for Spinoza, the basic building block of reality is whatever God is.
Spinoza also believed in determinism, that all actions and choices we make have been predetermined.

10. Dualism
Unlike monists, dualists say that reality does not consist of one, but rather two fundamentally different kinds of things: matter and mind.
There is a distinct physical world that can be experienced through the senses and a completely unrelated mental world that exists completely in the mind. These two categories of things are able to interact with each other.
French philosopher René Descartes (1596–1650 CE) developed the idea that the natural world consisted of material things (that interact with each other), but included an immaterial mind that was directly linked to the brain. He considered the fundamental nature or characteristic of the mind to be thought.

11. Cogito, Ergo Sum (I think, therefore, I am)...
“Next I examined attentively what I was. I saw that while I could pretend that I had no body and that there was no world and no place for me to be in, I could not for all that pretend that I did not exist. I saw on the contrary that from the mere fact that I thought of doubting the truth of other things, it followed quite evidently and certainly that I existed; whereas if I had merely ceased thinking, even if everything else I had ever imagined had been true, I should have had no reason to believe that I existed. From this I knew I was a substance whose whole essence or nature is simply to think, and which does not require any place, or depend on any material thing, in order to exist.”
-from The Discourse