Most of my apologetic encounters for the last 25 years or so have involved epistemology. So I've thought about epistemology a lot. Actually, I started thinking about epistemology long before I got interested in apologetics, and even before I had ever heard of the word, epistemology. I'm still not an expert in the sense that a professional philosopher might be an expert, but I think I have my epistemologgy worked out about as well as can be expected. I'm pretty confident in it, too, so let me lay it out in a nut shell.
I am a common sense realist, a weak foundationalist, and a particularist. There's some overlap between these terms, and maybe I'm using them incorrectly, but let me explain what I mean by them.
Common sense realism
I think I first heard this term as a description of a philosopher named Thomas Reid. I've also heard the term, "Scottish realism," and I think it's the same thing, but I'm not sure. Basically, it's just the idea that we should think the world is real because it at least seems to be real, and in the absence of any good reason to think it's not real, we should default to how things seem to be. That's the most rational position to hold--to affirm the obvious.
I'm part of a meet up group that gets together to talk about "hard questions" in culture, religion, philosophy, science, etc. There's a woman in there who sometimes describes herself as being a "meat and potatoes" persons. I like that. I told her I'm a meat and potatoes person, too. I think she's a common sense realist. When she says she's a meat and potatoes person, that just means she doesn't get all hung up on esoteric cunundrums in epistemology. She just takes the world in a common sense way, like just about all the common folk do. Of course there's an external world. Look!
I have often expressed this view as just affirming the obvious, which I think we all do most of the time. If things appear a certain way, we assume they are that way unless we have good reason to think otherwise. The most natural explanation for why it seems like there's an external world is because there is an external world.
Weak foundationalism
Here's where if any of my readers are professional philosophers, they're probably going to tell me how I've got it all wrong. But even if I'm using the wrong term, the important thing is that I accurately describe my point of view.
Foundationalism is the idea that all of our knowledge and beliefs rest on a foundation of axioms, unproven assumptions, or a priori knowledge. The foundation consists of actual items of knowlege. We know these things. We aren't just assuming them arbitrarily or for convenience. These foundational items of knowledge are our starting points. Everything else we know can be traced back to them or can be justified by them.
Aristotle once said something like, "Not knowing what requires demonstration and what does not argues want of education." He realized that there were some things we could know without proving and other things that require proof, and that an educated person ought to know the difference. It would be silly, for instance, to insist that somebody prove the laws of logic since you need the laws of logic to perform a proof in the first place. Our knowledge of logic shouldn't require proof.
But foundationalism comes in the strong and weak varieties. Strong foundationalism is the idea that all of the items of knowledge that belong in our foundation consist only of knowledge of necessary truths, analytic truths, and that sort of thing. Weak foundationalism is the idea that our foundational items of knowledge consist not only of necessary and analytic truths but also a handful of contingent and synthetic truths. An example of a necessary truth is that two plus two is four. An example of a contingent truth is that my senses are giving me true information about an external world that actually exists. While I think we can be certain about some truths--the necessary ones--we cannot be certain about the contingent truths. It's possible that there is no external world. It's possible that our senses produce perceptions that exist solely in the mind without corresponding to anything in the external world. But I nevertheless think our belief in the general reliability of our sensory perceptions is an item of knowledge. And there's a handful of other things I won't go into.
Particularism
I was introduced to particularism by J.P. Moreland in a talk I saw on the internet many years ago. He explained it by introducing me to the "problem of the criterion" and how there were two schools of thought on it. Well, actually, there are three. Let me see if I can explain this without botching it.
There are a lot of ideas that are all vying for our assent. Some of them are true, and some of them are false. We'd like to be able to sort them, but how do we begin?
One approach is called methodism. A methodist (not to be confused with the Christian denomination) thinks that we begin our quest for knowledge with a method. We sort the true from the false by using our method and applying some criteria or test to see what is true and what is not true. For example, we might adopt the method of observing with our senses. Or we might adopt the scientific method. Scientism is a version of methodism because people who subscribe to scientism think science is the only method for acquiring knowledge. But there are other methods one might use to distinguish the true from the false.
Another approach is called particularism. Instead of beginning with a method and working our way to items of knowledge, we begin with clear case examlpes of knowledge and work out a method. Having worked out a method, we can then use it to broaden our knowledge further.
I think that particularism is not only the correct approach, but it's the approach everybody actually uses whether they realize it or not. Methodism is self-refuting. It falls victim to what J.P. Moreland calls the "iteritive skeptic." An iteritive skeptic is somebody who just says, "Well, how do you know that?" every time you tell him how you know something. He's assuming that before you can know something, you first have to account for how you know it. And if you can't, then you don't know it. But this forces the methodist into an infinite regress. Since an infinite regress cannot be completed, the iteritive skeptic forces the methodist into global skepticism--that idea that we don't know anything at all.
The problem of the criterion is that before you can apply the methodist approach to knowledge, you first have to know at least two things. You have to know what criteria to use (or what method to use), and you have to know that such and such proposition either meets or doesn't meet the criteria. You have to know those two things before some proposition can become an item of knowledge. But then to know those two things, you have to have another criteria and be able to know whether or not those two things fulfill the criteria. So again, this leads to an infinite regress. Methodism makes knowledge impossible, which is why it's self-refuting.
And that brings me to global skepticism, which is the third approach. Global skeptics try to avoid the whole problem by just saying they don't know anything at all. Global skepticm is an untenable position for a couple of reasons. One reason is because it can never be rationally justified. Any reason or argument you give to try to justify global skeptism will depend on premises. But if you don't know anything, then you don't know that any of those premises are true or that your conclusion follows from those premises. So any attempt to justify global skeptism is going to end up being self-refuting as well.
Global skepticism is also untenable because there are obviously at least some things we know. At the very least, we know that we are thinking and that we exist, but if you're reasonable person, you're going to admit that you also know the earth orbits the sun, that a human can't live without water, and that murder is wrong (yeah, I said it).
If the only options are particularism, methodism, and global skepticism, and if methodism and global skepticism are untenable, process of elimination leaves us with particularism. With particularism, you just begin with a handful of what appear to be clear case examples of knowledge. For exmaple, I know that I live in Austin, Tx. I know I have a brother and a sister who both live here. I know that fire is hot. I know that if I strum my guitar, it will make a sound. But if you played a game of "How do you know that?" with me, I might eventually get stumped. There are some things I know without knowing how I know them. But if I think carefully enough about it, there's a chance I might be able to figure out how I know them. And once I do, I will have a new tool in my epistemological tool bag with which I can possibly learn new things.
As I said before, I think particularism is not only the right approach, but it's the epistemology pretty much all of us actually use in spite of whatever epsitemology we claim to use. If this were not the case, then there would be an awful lot of people in the world who don't actually know anything. Consider somebody with an IQ of 70. Even with an IQ of 70, people know who their siblings are. They know the sun is bright. They know it hurts to bump your head. There are lots of things they know. But if you asked them how they know, it probably wouldn't be difficult to stump them.
I remember when my daughter was around five years old, I asked her what colour her eyes were. She said, "Blue." I said, "How do you know they're blue?" She said, "Because I saw them in the mirror." I said, "Are you looking in the mirror right now?" "No," she said. "Then how do you know they're blue right now?" That might stump some five year old, but my daughter had an answer. She said, "Eyes don't change colour." But suppose I had stumped her. Would it follow that she didn't know what colour her eyes were? Of course not. She knew what colour her eyes were even if she couldn't fully account for how she knew.
You don't have to know how you know something before you can know it. If you did, then you'd fall victim to the iterative skeptic who could ask how you know that ad infinitum. Insisting that you must account for how you know something before it's an item of knowledge leads to global skepticism, and global skepticism cannot be rationally affirmed. If anybody really was a global skeptic, they wouldn't know it.
One criticism of particularism that's worth considering is that it allows people to just claim anything they want as an item of knowledge without having to justify it. I could claim to know that Santa Claus is an alien who lives on the moon if I wanted to, and if you asked me how I know that, I could just say, "I don't have to tell you how I know it. I just know it." While this criticism is worth considering, I don't think it ultimately goes through.
One reason it doesn't go through is because in reality, a person who said that about Santa Claus is probably just lying. An honest person isn't going to arbitrarily claim to know things he knows he doesn't know. Nevertheless, an honest person can rightly claim to know a few things even without being able to put his finger on how he knows exactly.
Another reason the objection doesn't go through is because being a particularist doesn't mean being infallible. There may be some things I think I know, but I don't really know them. And if I spend enough time trying to figure out how I know it, I may in the process learn that it's not an item of knowledge after all. That doesn't undermine particularism. I'm still going to begin with what appear to be clear case items of knowledge, even if I may be wrong about some of them.
Particularists don't claim that their "clear case items of knowledge" are beyond dispute. You can be a particularist, claim that your knowledge of the external world is a clear case item of knowledge, and be wrong about it. There is nothing inconsistent about that. But if you want to dispute a particularist's "clear case item of knowledge," it may not be enough to convince them that they can't prove it. You may have to disprove it before they'll budge.