When Pontius Pilate asked Jesus bar Joseph of Nazareth "What is truth?" he was voicing a question that he learned at the knee of his philosophy tutors. Truth is ephemeral and amorphous, for the philosopher. And it's crucial to understand what truth is, to be able to debate decisively. So what is truth, and how do we discover what is true?
Truth is reality. Quite simply, what is real is true, what is unreal is false. When I say that Keannu Reeves is a lamentable actor, that statement is real and depicts reality from my point of view. From another person's point of view, it is false. So, many statements can be true and false at the same time, depending on perception. But the definition of truth remains valid. The definition of truth, the need for the discovery of truth, is a crucial part of discovering what is reality.
Now, there are some statements which are completely true, from all perceptions. For instance, "Nothing unreal exists," is a complete truth because by definition, things that are real exist, things that are unreal do not exist. If words have meaning, then this statement is logically true. Here's another one. "Something unique cannot be duplicated." See? By definition, something unique is a singular thing. That means if you duplicate it, it stops being unique. How about this one, "If God exists, He is eternal." Now this is a conditional truth. That means that it is true if the first part is true. If the first part is not true, then the second part is also not true.
So, that's the first part of the question. What is truth? Truth is a declaration of reality. We now need to seek out the answer to our second question. How do we find the truth? Now, there are three ways of looking at this: logically, practically, and metaphysically. Logic is all about the mathematics of language, using symbols to depict reason. The practical discovery of truth has to do with leg work, physically going out and looking under leaves, so to speak. So let's look at the first way of looking for truth: logic.
LOGICAL TRUTH
Some statements are inherently true, demonstrable because of the definitions of the words. These statements we call axioms. To discover if something is an axiom, define the language, and see if there are no contradictions in the statement. For instance, if I say "Anything real exists," I can see from the definition of real and exist, that it is, by definition, true. That's an axiom.
A premise is a statement that presents evidence. For instance, "All banks are financial institutes." To discover if this is true, I must define the terms, do the research and find out if there are any banks that are not financial institutes. With a premise, we should be moderately suspicious and critical of the statement. It is not inherently true, and may, in some cases, be false.
Once we have two premises, we might be able to combine them into a true conclusion. For instance, "All banks are financial institutions," and "Wells Fargo is a bank." If these two premises are true we can arrive at a true conclusion that "Wells Fargo is a financial institution." This conclusion is true, because we started with true premises, and the conclusion follows the premises correctly.
A valid argument is a point of view that is based on an if/then statement that is internally logical. For instance, "If there is a God, then He is immortal." This statement is internally logical. If the first part is true, the the second part must be true. If the first part is false, then the second part must be false. It is a conditional premise. But a valid argument does not give us truth; it gives us two possibilities, one of which is true, the other false. So we need more. We need non-condition premises.
A sound argument, an argument that is true, is the combination of a valid argument and true premises. Here are a set of premises: "All banks are financial institutions. All financial institutions process home loans. Wells Fargo is a bank." For example, "If Wells Fargo is a financial institution, then it processes home loans." That's the argument. The premises lead to the conclusion that Wells Fargo is a financial institution, so it must process home loans.
The secret to finding truth in logic is to learn the various correct ways a premise leads to a conclusion, and, more importantly, to learn and watch for the logical fallacies that creep into arguments.
PRACTICAL TRUTH
The best way to discover whether a statement is true or not is research. If your husband says he was staying late at the office, the best way to discover whether that is a true statement is to call several people at the office and find out. If you come across a website that says ufo's landed in Roswell, the best way to determine the truth is to research the claims, the evidence and the eye-witnesses. There are two important factors in determining the truth in a practical sense.
"Extraordinary claims demand extraordinary evidence." If someone says they went on vacation to Cancun and, in evidence, they show you a blurry picture of someone at the beach, that is sufficient for us to accept as true. The statement is very likely to be true, so any evidence at all is sufficient. If someone, on the other hand, says they saw a ufo, and they show you a blurry picture of a white blob on a black background that might be a ufo in the sky, that evidence is not sufficient. Seeing a ufo is extraordinary. A blurry photograph is not extraordinary evidence. If they, on the other hand produce the alien or the spaceship so you can touch it, then you have extraordinary evidence.
"Extraordinary claims demand extraordinary corroboration." If you are surfing the web and you stumble across a webpage that tells you that their unique formula of agave and orange juice will extend your life, then you should demand extraordinary corroboration. If someone says that orange juice will cure your cold, and provides a whole bunch of names of people who've used orange juice to cure their colds, what you need to do before you accept this statement as true is do a little research. If you can find one reputable source that says that orange juice will not cure a cold, then you should accept the claim as false. Here's why.
Years ago, a psychic named Yuri Gellar did a great trick. He went on tv and said that he would mentally stop clocks all around the country. Thousands of people sent in their stopped clocks, proving that Yuri was a psychic right? Let's look at it. Yuri's claim is that he can stop clocks mentally. His evidence was thousands of examples of stopped clocks. But those two statements are not connected. Yuri says he stopped clocks on tv. You're watching tv, and hear this claim. You check your watch. Dang! It's stopped. You believe Yuri. But here's the problem. Your clock had stopped, whether or not Yuri said or did anything. You only checked to see if the clock was working at that moment because of what Yuri said. That means that Yuri Gellar got thousands of people to send in broken or unwound clocks. But He didn't stop them, he only got people to check. All the people who checked their watches and found them still running did nothing.
Yuri could never stop a single watch in the same room. He couldn't point to you and stop your watch. Even though it was a great trick, preying on human nature and a logical fallacy that connects two separate but unrelated events, if just one person had a watch that didn't stop, given this set up, his statement is false.
METAPHYSICS
How can we know if a metaphysical statement is true? For instance, God is real. I know this to be true. It is not a matter of belief; it is an undeniable and uttterly true reality. But how do YOU know that it is true. Obviously, I have discovered this truth, but you are wondering how you can also discover it.
In metaphysics, speaking of spiritual matters, there are obviously different standards of belief. Logical proofs are not so helpful when dealing with things that are inherently spiritual. Well, you have two options here. You can live or die according to logical proofs, or you can rely on faith.
LOGICAL PROOFS FOR THE EXISTENCE OF GOD
The hoary and ancient proofs for the existence of God are explained in great depth in other venues, so I will give only a short synopsis. The proofs of The Unmoved Mover, The Cosmological, The First Cause are all based on the idea that everything comes from something else, everything is caused by something that preceeds it. If that is true, then there must be something that is first, something that propels all other things into existence. It has to be metaphysical, because all physical reality obeys the logic of causality. Therefore, something outside of physical reality must be pre-existent. By definition, that is God. The Teteological Proof of God's existence tells us that complex things do not arise from simple things. All of creation is in the grip of entropy. If there are complex beings, like humans, that have arisen in this model, that means there is an engineer who is more complex than any creation who designed it. By definition, that is God. Finally, there is the Degrees of Goodness proof. This proof posits that since the human mind can concieve of an ultimate good, but cannot conceive of something that is so evil it could not be worse, that our brains have been hardwired to understand the concept of God. Now, this is a very brief summary of the proofs, and is in no way meant to be comprehensive. I do not have the space or desire to argue these proofs extensively. I present them as the logical alternative to faith.
FAITH
Saint Paul perfectly encapsulates the definition of faith when he tells us that faith is the evidence of things unseen, the proof of things that we cannot touch. Now, look at that statement carefully. Faith is not some kind of feeling. It isn't a generated illusion or delusion that we make up. Nope. Faith is independent of us. It is evidence of metaphysical things. Evidence does not exist in the mind, only. For instance, an eye-witness is evidence. An afadavit is evidence. A smoking gun is evidence. A fingerprint is evidence. But, when Oedipus says that Creon is guilty of treason because he knows it's true, that is not evidence. That's a delusion. Faith is evidence.
Faith is not some burning in your heart, because I get that when I eat something spicy. Faith is not logical arguments that prove God exists. Faith is not convincing yourself something is true, through human effort.
Here's what faith is, in terms of spiritual matters. Faith is the Spirit of God touching us personally so that we know He is real. Faith is the silent voice of God that speaks to us and assures us of His existence. Faith is God's gracious hand as it guides us. This is the evidence of God's existence that goes beyond physical reality to show us the metaphysical or spiritual truth that exists alongside of us. Faith is a very personal evidence because it is the very core of "seeing is believing." Faith is a personal evidence of God's existence that is undeniably real, so real that I make the statement, "God is real." I don't say "I believe God is real," because I may be wrong, if I say something like that. I used to believe in Santa, I used to believe that politicians were basically honest. I now understand that all those beliefs have changed. But God is real. This I know is true.