Surely knowledge is crucial in our day-to-day lives. We don't trust a dentist who believes he can perform a needed tooth extraction, no matter how sincere his belief; we go to a dentist who knows he can. We don't rely on a friend's hunch when wondering whether to take an umbrella; we listen to a meteorologist who has good reasons for his prediction. The prosecuting attorney (ideally) doesn't try to get the jury to feel angry with the defendant; she wants to establish the truth of his guilt.
Similarly, in matters of religion, what should matter is knowledge, not merely sincere belief; good reasons for faith, not hunches; truth, not feelings. Christianity is more than ritual or mythology or emotions; it is a knowledge tradition. Christianity claims certain things can be known.
Kinds of knowledge. We use knowledge (and the verb to know) in at least three different senses. It refers to (1) propositional knowledge-knowing facts; (2) knowledge by acquaintance-knowing something or someone directly; and (3) skill knowledge-know-how.
Here are some examples. A sports fan' may know many facts about last year's MVP, or a historian may know all about ancient Rome, and yet neither' person's propositional knowledge constitutes the direct knowledge by acquaintance that the player's teammates or Julius Caesar possessed. Someone may have the know-how to ride a bike or play pool without having any propositional knowledge about force, inertia, or angular momentum.
Christianity involves all three types of knowledge. Eternal life, Jesus said, is knowing God (Jn 17:3). This is knowledge by acquaintance and is more than knowledge of Bible facts or systematic theology. (Sadly, it is possible for someone to know a lot about the Bible, or a lot about theology, and yet not know God.) Jesus went on to say that eternal life is knowing "the One You have sent-Jesus' Christ." This involves knowing certain facts about Jesus of Nazareth and about His mission as Savior. So both knowledge by acquaintance and propositional knowledge are involved.
What about skill knowledge? Since salvation is not by works, no skill is involved in becoming a Christian. But growing in our faith involves learning certain skills: how to study the Bible, how to think as Christians about decision making, how to pray, how to share our faith, and so on.
Propositional knowledge. All three senses of knowledge are important, but propositional knowledge demands careful consideration. For the vast bulk of what we know is propositional and does not come by direct acquaintance or know-how.
Propositional knowledge may be defined roughly as justified true belief. First, obviously, you can't know something if you don't believe it. Second, the proposition you believe must be true if it is to count as knowledge. Sincere (but false) beliefs, even useful (but false) beliefs, are not knowledge. Third, a true belief must be justified; that is to say that you must have the right kinds of reasons for the belief. Even true beliefs do not count as knowledge if they are the result of a lucky guess, a hunch, or a passionate wish that things be so. The right kinds of reasons are those making it probable that the proposition you believe is true. They are truth indicators.
What counts as the right kinds of reasons depends on the nature of the proposition. I believe the sun is shining because I can see it and feel its warmth. I believe I had cereal for breakfast because I clearly remember it. I believe my wife loves me because she tells me so, she shows me in many ways, and she has stuck with me for a number of years. And I believe Tiglath-pileser was a mighty king of Assyria who invaded Israel in 743 B.C. because I read about him in the Bible (2 Kg 15-16) and in reliable histories of Assyria. In all these cases the reasons why I believe what I do are truth indicators. They are the right kinds of reasons to justify those beliefs.
Can we know anything without using our senses? In the examples above, the justifying reasons involved the senses-even beliefs based on memory, for the memories were formed through sensory experiences. It is clear that beliefs based on our senses can be justified (provided, of course, that we are not too tired, the lighting is adequate, our sense organs are functioning properly, and so on). Knowledge based on the senses is called empirical knowledge.
The Enlightenment doctrine of empiricism holds that all knowledge of the world is empirical. Today, the spectacular successes of the natural sciences have enshrined empirical investigation as by far the best-and for most people, the only-way to now. But what about things we can't sense? Is nonempirical knowledge possible? The question is crucial, for a great many important things can't be known through our senses-things such as whether we have a soul and whether God exists.
Is empiricism true? No. Notice first that the claim "All knowledge of the world is empirical" is itself not an empirical statement. How could we know that through our senses? The claim is self-refuting. But beyond that, there are good reasons to think that at least some knowledge of the world is nonempirical (a doctrine called moderate rationalism). Beliefs that certain things exist that cannot be directly observed may be inferred from empirical observations. This is how we justify belief in such things as electrons, gravitational fields, beauty, or love. And similarly for belief in God. Further, the analogy between sensory experience and religious experience provides good reasons for the justification of religious beliefs based on religious experience.
Finally, we can know some things without using our senses at all. For example, we can know much about ourselves through introspection (a nonempirical process). We can know that we have minds that think, believe, hope, fear, and so on, and that we are not identical to our bodies. Many ethicists claim that moral knowledge is accessible through intuition or conscience or pure reason. Following St. Anselm, many scholars have thought that the ontological proof-a nonempirical argument-establishes God's necessary existence. Moreover, we have nonempirical as well as empirical evidence of God's existence (Rm 1:19-20), what has been called the sensus divinitatis. And since our belief in God's existence is justified, we also are justified in believing what He has revealed to us. For all these examples, we can point to the right kinds of reasons that justify nonempirical beliefs.
Extracted from the Apologetics Study Bible.