Christians have, for some time now, been accused of a lack of reason. Typically, the way things are portrayed, people like to make it seem as though faith and reason are opposites and therefore are incompatible. Sadly, even those within the Church are often convinced of this.

I’ve written before about this and still feel the same when it comes to the faith vs. reason argument.

Not to worry, I’m not going to re-write that post again. Instead, what I wanted to do today was go a little more in depth on the idea of reasoning. What I wanted to go over today was the fact that there are, currently identified and defined, three distinct methods of reasoning.

That’s right, there are three different ways to use reasoning. They are deductive, inductive and abductive. And I’d like to take some time to discuss these three types of reasoning that we use and how/when they are typically used.

The first one, deductive reasoning, became quite popular with Sir Arthur Conan Doyle’s Sherlock Holmes character. While, after having read some of the Sherlock Holmes stories, I’m not sure that “deductive reasoning” is the best fit for him, that’s what I’ve always heard it described as. So, exactly what is deductive reasoning?

First of all, deductive reasoning is the only one of the three types of reasoning that results in a certain conclusion provided that the information used to derive your conclusion is true and accurate. One example of deductive reasoning is mathematics. If x = 1 and y = 2, we can deduce that x + y = 3. The statements “x = 1″ and “y = 2″ are called “propositions” or “premises.” If these two premises are true, we can be 100% certain that our “conclusion” of “x + y = 3″ is true.

This type of reasoning relies on knowledge and information that we already know (or at least can know). Because of this, there is no way to increase human knowledge using deductive reasoning. Certainly, it is still quite useful. However, it is limited.

Another limitation is that deductive reasoning is unable to allow us to predict the future. Mainly because it relies on observation of existing propositions. Once you propose something hypothetical, even if it as based heavily on what you know or have concluded using deductive reasoning, you are now moving into one of the other types of reasoning.

Next, let’s look at inductive reasoning. This type of reasoning is often the type of reasoning used by scientists.

That may surprise you as the media has a tendency to portray science as being absolutely certain of things that scientists themselves, were you to look at their own claims, are not quite as certain of. I believe that this is a big part of the reason why so many people in the scientific community are non-believers. They are skeptical by nature…about pretty much everything. Not only of many of their own conclusions, but also of God’s existence.

With inductive reasoning, we cannot be 100% certain of our conclusions. That is because inductive reasoning uses existing knowledge to pose a hypothetical truth.

This is one method by which human knowledge increases. We take the knowledge we have, develop a hypothesis, test the hypothesis and draw a conclusion based on the results. Even then, however, most of the scientists who have a successful experiment will claim that their hypothesis is not necessarily “proven.”

Instead, you will hear them say things such as “What we have observed is…” or “In our tests, the results have shown that…” but they often will not just come right out and say “This is how this works” or some such thing.

The fact is, when using inductive reasoning, one reason we cannot know our conclusion with complete certainty is because there is the possibility that there is data or information that has not been taken into account.

Building on our math example in a more practical application, let’s say you want to put topsoil in your yard. You measure the length and width of the yard to get the square footage and then go to the store to buy your soil. You have some good information. Very useful information. With it, you could figure out a pretty good number of bags of soil to buy. The problem is, you don’t know how deep you need the soil. So, while you can be reasonably certain you’re buying enough, you could be wrong.

The final type is abductive reasoning. To be honest, this one is a bit newer to me. The most concise way to describe abductive reasoning is that you are drawing the conclusion that best fits the evidence or information you have. Unlike inductive reasoning, this is used when you already actually know that you don’t have all the facts, but must draw a conclusion based on what you have.

Where I first heard of this type of reasoning was from Jim Wallace of Please Convince Me. Jim is a cold-case homicide detective in southern California. He uses abductive reasoning all the time in his professional career.

Because he works on cold-cases (unsolved crimes that are no longer being investigated unless someone like Jim pulls the files and starts to investigate…usually cold-cases are very old and often involve witnesses, victims and possibly perpetrators who are no longer alive), Jim often has to go by whatever evidence he has as, many times, more evidence is impossible to obtain.

As with inductive reasoning, abductive reasoning cannot draw conclusions which are 100% certain. Also, like inductive reasoning, abductive reasoning is capable of increasing  human knowledge. Another thing that abductive reasoning is useful for is, imagine me bringing this up, drawing conclusions about the Christian faith.

Let’s face it, the claims of Christianity are very much like a long-term cold case. None of the original eye witnesses are alive. Very little physical evidence is available and I’m not sure than any of it is direct physical evidence. We don’t have blood samples, DNA, photographs, etc.

What we have is historical evidence, written accounts by eye witnesses and some archaeological evidence that really does little more than help us trust the written accounts to be reliable by showing that names, places and dates described in the written accounts match up with what is found.

In the grand scheme of things, however, we know that there is a lot of information that we don’t have. But, with all the evidence we do have, we can reasonably draw the conclusion of the truth of the claims of Christianity by looking at the evidence we have and determining what explanation fits the most facts with the lease amount of “creative gymnastics” if you will. Perhaps next week, I’ll go into a bit more detail on that.

For now…

Grace, love and peace.