All of us (or at least most of us) have beliefs about what exists: the universe, time, living beings, we humans and our place within the cosmos, etc. These individual entities or concepts that we believe in, however, normally do not exist in a vacuum without interrelation. Instead, we construct systems of belief, where things fit together into a “big picture” explanation of reality. This big picture makes up our metaphysical beliefs.
As Austin Cline of About Agnosticism/Atheism explains:
“In Western philosophy, metaphysics has become the study of the fundamental nature of all reality — what is it, why is it, and how are we can understand it. Some treat metaphysics as the study of ‘higher’ reality or the ‘invisible’ nature behind everything, but that isn’t true. It is, instead, the study of all of reality, visible and invisible; and what constitutes reality, natural and supernatural.”
Many atheists often eschew metaphysics as one of those arcane subjects of philosophy, which asks pointless and untestable questions about reality. However, as Cline explains:
“Because metaphysics is technically the study of all reality, and thus whether there is any supernatural element to it at all, in truth metaphysics is probably the most fundamental subject which irreligious atheists should focus on. Our ability to understand what reality is, what it is composed of, what ‘existence’ means, etc., is fundamental to most of the disagreements between irreligious atheists and religious theists.”
One way to think about metaphysics is that, even if science (or some epistemology of the sort) informs our beliefs about what exists, metaphysics is concerned with finding a place for what exists within a broader philosophical and theoretical framework. Metaphysics is concerned with fitting the pieces together.
For example, we can agree that time exists, but what really is the nature of time and what is it like? Is the present the only moment that is real, or is all of time equally real? How does time relate to space? How does time fit in with the rest of our picture of the universe? As will be explored below (in discussion about the A-theory and B-theory of time) these are metaphysical questions. We have to form a metaphysics of time in order to understand how it fits into our broader theories about the universe and reality.
Thinking about metaphysics and how to fit the pieces together is important, since religious apologists (often following CS Lewis’ straw man style of attacking atheism) will frequently claim that certain things are incompatible with an atheist or naturalist view of reality. Apologists will claim that atheists can have no basis for morality, for example, or that we could never have the reliable truth-finding faculties to know that atheism is true without God.
These types of questions, however, are metaphysical questions. The real issue is whether or not morality can be fit into a naturalist theory of the universe, or whether there is an explanation for how reliable truth-finding faculties could come about in a naturalist universe. These metaphysical questions can be answered, for one who stops to really think about them. While apologists frequently raise such challenges in an effort to end the conversation there and declare that atheists have “no answer,” for serious philosophers it is only the beginning of the inquiry.
Philosophers, such as Jack Ritchie in Understanding Naturalism and Richard Carrier in Sense And Goodness Without God, have developed and defended a sophisticated metaphysical view called metaphysical naturalism. Metaphysical naturalism seeks to explain every feature of our reality through only natural entities and causes, without the need of god(s) or the supernatural in any part of one’s worldview and life philosophy. In other words, a “big picture” explanation of reality can be reached without any appeal to religion, making religions such as Christianity or Islam unnecessary and extraneous to answering the big questions in life. As professional philosopher Graham Oppy explains in The Best Argument Against God, if metaphysical naturalism is true, then theism is consequently false.
As such, understanding metaphysics and being able to defend metaphysical naturalism is the best way to defend irreligion and atheism against the attacks of religious apologetics. This page works to lay out a description of what the “big picture” looks like under the metaphysical naturalist worldview.
Below is a blog series about the ‘metaphysics’ in metaphysical naturalism, which looks into a broad range of metaphysical issues in philosophy, including the following:
- Defining the ‘Natural’ 
- Cosmology and Time
- Evolution and Human Origins
- Agency and Freewill
- Consciousness and Epistemology
- Analytical vs. Synthetic Knowledge
- Particulars, Universals, and Abstract Objects
- Meta-Ethics and Normative Ethics (part 1)
These slots will be filled as new essays on these topics are posted. As can be seen, the first slot, “Defining the ‘Natural’,” is already filled in, linking to our first discussion!
 For an additional article on defining the ‘supernatural,’ see here.