“HOW IS TRUTH KNOWN?
Let’s sum up what we’ve seen so far: truth exists, and it is absolute and undeniable. To say “truth cannot be known” is self-defeating because that very statement claims to be a known, absolute truth. In fact, anytime we say anything, we are implying that we know at least some truth because any position on any subject implies some degree of knowledge. If you say that someone’s position is wrong, you must know what is right in order to say that (you can’t know what is wrong unless you know “what is right). Even if you say, “I don’t know,” you are admitting that you know something; namely, you know you don’t know something else about the topic in question, not that you don’t know anything at all.
But just how does one know truth? In other words, by what process do we discover truths about the world? The process of discovering truth begins with the self-evident laws of logic called first principles. They are called first principles because there is nothing behind them. They are not proved by other principles; they are simply inherent in the nature of reality and are thus self-evident. So you don’t learn these first principles; you just know them. Everyone intuitively knows these principles even if they haven’t thought about them explicitly.
Two of these principles are the Law of Noncontradiction and the Law of the Excluded Middle. We’ve already seen the reality and value of the Law of Noncontradiction. The Law of the Excluded Middle tells us that something either is or is not. For example, either God exists or he does not. Either Jesus rose from the dead or he did not. There are no third alternatives. “These first principles are the tools we use to discover all other truths. In fact, without them you couldn’t learn anything else. First principles are to learning what your eyes are to seeing. Just as your eyes must be built into your body for you to see anything, first principles must be built into your mind for you to learn anything. It is from these first principles that we can learn about reality and ultimately discover the box top to this puzzle we call life.
Although we use these first principles to help us discover truth, they alone cannot tell us whether or not a particular proposition is true. To see what we mean, consider the following logical argument:
1. All men are mortal.
2. Spencer is a man.
3. Therefore Spencer is mortal.
The self-evident laws of logic tell us that the conclusion, Spencer is mortal, is a valid conclusion. In other words, the conclusion follows necessarily from the premises. If all men are mortal and if Spencer is a man, then Spencer is mortal. However, the laws of logic do not tell us whether those premises, and thus the conclusion, is true. Maybe all men are not mortal; maybe Spencer is not a man. Logic by itself can’t tell us one way or the other.
This point is more easily seen by looking at a valid argument that isn’t true. Consider the following:
1. All men are four-legged reptiles.
2. Zachary is a man.
3. Therefore Zachary is a four-legged reptile.
Logically, this argument is valid, but we all know it isn’t true. The argument is valid because the conclusion follows from the premises. But the conclusion is false because the first premise is false. In other words, an argument can be logically sound but still be false because the premises of the argument do not correspond to reality. So logic only “gets us so far. Logic can tell us that an argument is false, but it cannot tell us by itself which premises are true. How do we know that Zachary is a man? How do we know that men are not four-legged reptiles? We need some more information to discover those truths.
We get that information from observing the world around us and then drawing general conclusions from those observations. When you observe something over and over again, you may conclude that some general principle is true. For example, when you repeatedly drop an object off a table, you naturally observe that the object always falls to the floor. If you do that enough, you finally realize that there must be some general principle in place known as gravity.
This method of drawing general conclusions from specific observations is called induction (which is commonly equated with the scientific method). In order to be clear, we need to distinguish induction from deduction. The process of lining up premises in an argument and arriving at a valid conclusion is called deduction…the process of discovering whether the premises in an argument are true usually requires induction.
Much of what you know, you know by induction. In fact, you’ve already used induction intuitively to investigate the truth of the premises in the arguments above. Namely, you determined that since every man you’ve observed has been a two-legged mammal, the man Zachary cannot be a four-legged reptile. You did the same thing with the question of Spencer’s mortality. Since all men you’ve heard about ultimately die, you made the general conclusion that all men are mortal including a specific individual man named Spencer. These conclusions—two-legged men, gravity, and human mortality—are all inductive conclusions.
Most conclusions based on induction cannot be considered absolutely certain but only highly probable. For example, are you absolutely, 100 percent certain that gravity makes all objects drop? No, because you haven’t observed all objects being dropped. Likewise, are you absolutely certain that all men are mortal? No, because you haven’t observed all men die. Perhaps there’s someone somewhere who hasn’t died or will not die in the future. “So if inductive conclusions are not certain, can they be trusted? Yes, but to varying degrees of certainty. As we have said before, since no human being possesses infinite knowledge, most of our inductive conclusions can be wrong. (There is one important exception. It’s called the “perfect induction,” where all the particulars are known. For example, “all the letters on this page are black.” This perfect induction yields certainty about the conclusion because you can observe and verify that every letter is indeed black.)
But even when we don’t have complete or perfect information, we often have enough information to make reasonably certain conclusions on most questions in life. For example, since virtually everyone has been observed to die, your conclusion that all men are mortal is considered true beyond a reasonable doubt; it’s 99-plus percent sure, but it’s not beyond any doubt. It takes some faith—albeit a very small amount—to believe it. The same can be said for concluding that gravity affects all objects, “not just some. The conclusion is practically certain but not absolutely certain. In other words, we can be sure beyond a reasonable doubt, but not sure beyond all doubt.
Excerpt From: Norman L. Geisler & Frank Turek. “I Don’t Have Enough Faith to Be an Atheist.” Crossway Books. iBooks.
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Within the next post we will look at how the truth about God can be induced, and to a very high degree of certainty, known.