Most theists are not "plain theists". Rather, they embed their theism within a wider worldview perspective such as Christianity, Islam, or deism. By the same token, most atheists are not plain atheists. Instead they embed their atheism within a wider worldview perspective: that which is commonly called "naturalism". As such, it is worthwhile not only for the theist to critique atheism as a claim, but also to evaluate the justification for the naturalistic worldview in which atheism is typically embedded.

So what then is naturalism? This is a fascinating and very difficult question to answer. While naturalists debate over the best way to define their position, here is one way that naturalism is commonly defined:

Naturalism: "the view that the only things that exist are matter and energy and that which supervenes upon matter and energy."

The first part of the definition is clear enough. We all have a basic understanding of matter and energy. But what does it mean to "supervene upon"? Perhaps the easiest way to explain the concept of supervenience is by way of an example, so here goes. Neither hydrogen atoms nor oxygen atoms have the property of wetness. But combine them to form water and the property of wetness comes to exist as a result of the combination. It arises from them and is irreducible to them. In other words, wetness supervenes upon the atomic structure of the combined hydrogen and oxygen atoms.

Thus the naturalist is one who says that everything that exists is either reducible to matter/energy (like hydrogen and oxygen atoms) or is supervenient upon matter/energy (like the property of wetness which arises from but is irreducible to the combined atoms). Incidentally, this is remarkably like the ancient Greek philosopher Democritus' view that all that exists is "atoms and the void." Naturalism, it would seem, has been around for awhile.

It follows that if one adopts a naturalist's view then one denies that anything could exist which does not ultimately derive its existence from matter/energy. And this includes a range of non-material based supernatural entities like souls, angels, and of course God.

But why think that naturalism is true? Why think that the only things which exist are matter, energy, and that which supervenes upon matter and energy? What justifies this worldview?

There are two ways that one could possibly justify naturalism. The first and stronger way is a priori. That is, one could argue in principle or by definition that only matter, energy and that which supervenes upon matter/energy could exist. But a very high threshold of evidence would be demanded to justify the naturalist worldview a priori. What argument is there which demonstrates in principle that souls, angels, and God could not exist? Alas, I am aware of none.

This leaves the naturalist to argue for the weaker a posteriori course. According to this empirical approach, while supernatural entities could in principle exist, empirical enquiry yields no evidence of them.

I take issue with the empirical naturalist's claim because I believe there is substantial evidence for the existence of supernatural entities. But let's leave that aside. Instead, note that the naturalist has now painted herself into a corner. By adopting this weaker empirical approach, the naturalist loses her justification for holding naturalism (at least as defined above). In short, now she cannot claim any longer that the only things that exist are matter, energy and that which supervenes on matter and energy. Instead she should adopt the view that she does not know.

Sadly, naturalists typically continue in their naturalism even though they have no evidence to justify its central claim. What is doubly sad is that many seem to have convinced themselves that naturalism is the only scientifically respectable position. But what is scientific about making a dogmatic declaration that is not justified by the evidence? This looks rather like what atheist Richard Dawkins derisively calls a "faith-head".

**I'm leaving today for a weekend in the mountains (Banff, Alberta). Have a good weekend :)