Before I launch into all that I have to say about things, I think it only fair to let you know how I think. How I determine what is true. My epistemology, if you will. It's pretty simple, in the end, so you be the judge if it makes sense or not.
If you read any philosophy at all you will quickly see that different philosophers throughout history have started in various places in their search for truth. I have read a lot of philosophy (but still only a tiny fraction of what's out there) and frankly, I find most of it wanting. So rather than try to critique different philosophers like Descartes, Hume, Kant, and so on, I will present my point of view and just take cheap shots at the "dead white guys" when it suits me. I need to do this because these men (Descartes not so much) still have influence today even though their thinking is deeply flawed. You may be wondering "who are you to be critiquing famous philosophers that are still read centuries after they died?" Well, that's a good and fair question. My answer is that in the end you will just have to judge for yourself if I make my case or not.
After much thinking about it, I have decided that the place to start is at the beginning. That is more profound than you might think at first blush. Unfortunately, I'm not the first guy to figure that out (see Aristotle), but rather than try to explain him, I'll just explain me. There is no claim to originality here. Perhaps some synthesis at most. I think I have had two original ideas in my whole life so far and I will let you know, with great fanfare, no doubt, what they are when the time comes.
(As an aside, if you read a lot and think a lot about what you read, then you will have many "a ha" moments. Moments of discovery when you, well, maybe not you, but I, think, I just had an original idea. No one has ever thought of that before. It's exciting but unfortunately, almost every time I subsequently read something else soon after where the author not only has thought of what I thought but explained it much better than I ever could. Damn them. Except for those two times.)
I think the place to start in our quest for knowledge is with what we cannot deny. In other words, I think it best if we build our foundation of knowledge on rock solid truths that are literally undeniable. (Everyone knows them even if they are ignored or suppressed.) So if we start with undeniable principles, and reason correctly from there, we should have a pretty good shot at arriving at the truth. But, you say, reason isn't enough, we need data, or facts, or empirical evidence, too. That is correct. There have been people in the past who said that reason is the only way to knowledge (I'm grossly oversimplifying here) and there have been people who say that the only way to knowledge is by sense experience. The former are called rationalists and the latter are called empiricists. They both have a point, but coming to the truth requires BOTH reason AND empirical (sense experience) evidence.
So what are these truths? Again, with apologies to Aristotle, I think we start with what we cannot deny. So what can we not deny? The first thing is that we exist. If you exist, then the most fundamental thing you can say about yourself is that you exist. It's undeniable because in order to deny your existence you would have to exist. I hope at this point, we are all still in agreement. So we exist. Let us abstract from the fact of our existence that "existence is." Or we may say "Being is." This is the fundamental ontological claim that can be made. So what else do we know that is undeniable?
We know that we are who we are. We have identity. I am I and you are you. This may seem ridiculously simple minded to you but please, please bear with me because you will see later on that many people today who loudly proclaim "truth" routinely deny these fundamental principles. We may also describe Identity by saying that "Being is Being." A thing is what it is, in the common tongue.
So we know that we exist (Being) and we know who we are (Identity). These are called First Principles of reasoning. Being and Identity. They are undeniable. They are known by everyone (with a normal mind). They also are not material. (This will be HUGE later on.) They also are therefore not explainable by physics or chemistry or biology. (This will also be HUGE later on.)
Now, if these first two principles are true, and they are, we can state them in a little different way which will be more useful to us. I like to say: "There is a way that things are." "There is a way" is another way of saying Being and "that things are" is another way of saying Identity. We can see immediately that this is an acceptable way to express Being and Identity because it is impossible to deny that "there is a way that things are." It's impossible because if I deny that there is a way that things are, I am, in fact, claiming that there is a way that things are. Perhaps this is a bit too abstract so let me illustrate with a concrete example. If I claim that the way things are is that God exists and you say that is not so, then you are claiming that there is a way that things are that God does not exist. In either case, THERE IS A WAY THAT THINGS ARE. I hope I have made this crystal clear because it is so important. It is important because it is, as far as I can tell, the fundamental ontological truth upon which all other truth is based.
Now, you may be thinking, well so what. What have you really said so far? After all, I don't know a thing about HOW THINGS ARE. Granted, but we are just getting started so again I beg for patience. There is a distinction that needs to be made here and perhaps now is the time. Ontology (the study of what exists, or being, if you will) is different from epistemology (the study of knowledge, what we can know and how we can know it). Unfortunately, this fundamental difference is often ignored and as a result, contemporary "intellectuals" (an intellectual being someone who writes a book about philosophical or scientific things - in other words, not me) often say some really, really stupid things. Let me give you an example. In the field of ethics, which is notorious for this kind of thing, and I will argue strenuously for my example later, people often say something like: "well in this situation I do not know what the right thing to do is, so... (here it comes) there must not be a right thing to do." NO. NO. NO. The fact of the matter is that THERE IS a right thing to do but maybe we just don't know what it is. That is the difference between ontology and epistemology. There is a right (and wrong) because there is a way that things are (ontology).
Just because we may not know what that is in some, or many, circumstances, just means that we don't know (epistemology). It doesn't mean that right and wrong, for example, don't exist. This confusion is profound, as we will see, and it is also pervasive in some circles where people should know better. You don't have to accept, at this point, that right and wrong exist, I haven't made that case yet. I merely used it as an example to illustrate the confusion that often exists between ontology and epistemology. I could have used a different example, in fact, let's do that. Let's say that just because physicists have not yet discovered a way to unify quantum field theory and gravity that there is no unification to be had. But this seems clearly false to me because there is a way that things are and they can't be different in the same universe. So this is an epistemological issue and not an ontological one.
Now if you are observant, you will have noticed that I just made an assertion for which I gave no arguments, or reasons, for its truth. I said that there is a way that things are and they can't be different in the same universe. What I mean by that, and I hope this is a good way to get back to First Principles because we are not finished with them yet, is that if there is a way that things are, then, we know, by immediate inference, that is, no further reasoning is required, that there is a way that things are not.
How do I say that? If Being is Being, and it undeniably is, then we must immediately know that Being is not also non-Being. I hesitate to get too pedantic here but this is the crucial and most fundamental rule of logic (or reason, if you prefer) so if I insult your intelligence in the next few sentences it is only out of necessity. Let me say it again in a slightly different way. Being cannot be non-being. Something cannot BE, and NOT BE, at the same time and in the same way. This should not require a lot of reflection. Let me say it with a couple of examples just to make sure we are clear on this. A "1" cannot be a "2." Because a "1" is a "1" and a "2" is a "2" (or to follow the syntax of my claim, a "2" is a specific instance of a "not 1.") So it is impossible for a "1" to be a "1" and a "not 1." It is impossible for me to both exist and not exist. You can't have a million dollars in the bank AND not have a million dollars in the bank. It is impossible for God to exist AND not exist. I use the word impossible in a literal sense. It is not possible for opposing truth claims to both be true.
Okay. This is called the law, or principle, of non-contradiction and it is absolutely critical and necessary that we are all on the same page with this. Because this is part of the foundation. We have to start in a place where we agree and we must agree on first principles because they cannot be denied. That's the thing about first principles, they are FIRST in the chain of reasoning. There is nothing prior to them. We all know them because we all experience them directly with our minds. They are apparently built in to the structure of our minds because every normally mentally functioning human being knows them regardless of language, sex, culture, race, or whatever. At the risk of offending you one more time let me explain one more time in a little different way why the law of non-contradiction is undeniable. Here is perhaps an easier way to say that Being cannot equal non-Being. Let's say that "opposing truth claims cannot both be true." That's another way of expressing the law of non-contradiction. Opposing truth claims cannot both be true.
So how is that undeniable? Here's how. If I say that opposing truth claims can be true AND not true, what am I saying? First I am saying that they can be true and not true, but I am also saying that they cannot be true and not true. Thus my statement is self-contradictory and therefore false. I'll tell you how powerful these laws of Reason are. Even God, should He exist, can not do something logically impossible. Even God cannot make 1 = 2. Or, for the empiricists (scientists), an electron cannot be an electron and a photon at the same time and in the same way. The speed of light in a vacuum cannot be (approximately) 186,000 miles per second and not be 186,000 miles per second. The laws of thermodynamics cannot be true and not true. Well, I trust that we are all on the same page so far.
The law of non-contradiction is closely connected to our next bit of immediate inference which is that something either exists or it doesn't exist. There is no middle ground. Either being or non-being. Either 1 or not 1. Either true or not true. Either, well, you get the point. This point is called the law, or principle, of the excluded middle and it goes hand in hand with the law of non-contradiction. Opposing truth claims cannot both be true and a truth claim cannot be both true and false. In fact, it is either true or false. Concerning all truth claims, true and false are the only two possible answers in an ontological sense. We may not KNOW which is true and which is false but in all truth claims, the answer is either true or false. I hope this makes sense. I will have more to say about First Principles later but for now let's summarize.
Principle 1. Being is. This is called the law or principle of Being.
Principle 2. Being is Being. This is called the law or principle of Identity.
Principle 3. Being cannot be non-Being. This is called the law or principle of non-contradiction and it can also be expressed as "opposing truth claims cannot both be true."
Principle 4. Either Being or non-Being. This is called the law or principle of the excluded middle. It means that EVERY truth claim is either True or it's not.
If we can agree on these, and I don't see how we cannot, then I can continue with the remainder of my epistemological stance. Or, said plainly, how we can know what is true. But not tonight.