Why Naturalism is Inherantly Non-sensical
There is an excellent book by Notre Dame philosopher, Alvin Plantinga called, "Where conflict really lies," in which Plantinga talks about the rationality of our brains. Humans have to assume our brains work. Comedian Brian Regan has a bit where space men go looking for intelligent life but only find unintelligent life. They get off the space ship, see aliens walking around with dumb looks on their faces who say, "2+2= Chicken!"
2+2=chicken is a good example of a brain that does not work. In contrast, when we humans say, 2+2=4, we assume that is a meaningful statement. We assume that our brains work well enough for that. And a lot of other things. We debate things. We reason things. We gather evidence. We draw conclusions. We assume that these are all valuable things to do. We think our brains work. We acknowledge limitations (sometimes we forget things, sometimes we misunderstand, etc) but to even attempt to learn, discuss or debate, we have to assume a certain level of rationality of our brains.
But Plantinga notes, this is impossible to prove. As soon as we use logic, reason, evidence or arguments to prove that our brains work, we assume the conclusion. If our brains didn't work, the logic, reason, evidence, and argument we make might be no more meaningful than 2+2=chicken.
There is no non-circular way to prove rationality.
So... is it rational to believe we are rational?
Plantinga says.... maybe.
He explains that it is rational to assume something if there not a good reason to doubt it. He uses this illustration (I paraphrase).
A man walking by a field and sees a white fluffy animal on the hill and thinks, 'that is a sheep.' He goes into town and sits down in the bar continuing to assume he has seen a sheep. At this point, he is perfectly rational. But suppose the farmer who owns that land happens to be sitting next to him and says, 'no, I don't have any sheep. I do have a big fluffy white dog though.'
At that point, for the man to continue to assume that the sheep was a sheep is irrational. The only rational way to continue to believe that he saw a sheep would be to go back to the field, climb the hill, and look at the animal. It is possible it was a sheep but the assumption of sheep is no longer rational.In this illustration, the sheep represents rationality. And the farmer represents our world view (how we make sense of the world). Plantinga says that naturalism is a worldview (a farmer) who asserts that there is no sheep in that field. He explains that unguided evolution (no God, no Spirit, no Divine) is a farmer who owns no sheep. The universe is full of irrational beings. Trees, bacteria, fish, mushrooms, dogs, and spiders are all the products of natural selection and absolutely none of them are able to distinguish between 2+2=4 and 2+2=chicken. Not a single one. And that is because evolution does not select for rationality. It selects for survival. It is possible to imagine certain times when rationality might help survival but there are other times when rationality would hinder survival.
If I see a lump in the forest, it is better for me to irrationally assume it is a bear and run away than to rationally evaluate it as the lump gets closer and eyes me for food. Most things evolution created survive very well without any rational thought whatsoever. Some things survive precisely due to irrationality.
In fact, if evolution made us rational, we are the only known product of the process to utilize rationality for survival. Possible. But hardly something you could assume. It is the sort of thing we would need to prove to believe. We would need to go back to the hill and get a good look at the sheep. Which is impossible because there is no non circular way to prove rationality. We can't get back to the hill. The farmer is saying, 'there is no sheep on that hill' and we cannot go back.
In contrast, most religious world views have a farmer who either says nothing about the sheep or affirms that he does indeed own sheep. For example, the Christian worldview says that God is rational and created humans in his image. We are rational because God created us rational. Christians can merrily assume rationality and do so rationally. Our farmer owns sheep. And just as the man who thought he saw a sheep is rational for assuming it was a sheep (and even more so if the farmer next to him agrees that it was a sheep), it is perfectly rational for Christians to assume that we are rational. We can move on to higher forms of knowledge (science, logic, etc).
So, naturalism, Plantiga argues, is in direct conflict with rationality. It is inherently irrational to assume you are rational. Unguided evolution makes such an assumption highly unlikely. So, when it comes to science and intellectual discovery, only one world view is in direct contrast. Naturalism. There is no rational way to argue for naturalism. It is fundamentally irrational.