One of the most important aspects of the Creation/Evolution debate is the definition of “science.” It is generally assumed that there is one definition of science but this is simply not true. In fact there are many definitions of science and an entire branch of philosophy dedicated to the study of the definition of science. Even so, it is critical to learn to distinguish between two very different types of sciences, Operational Science and Historical Science (or what is often called Origin Science). The dramatic confusion that most people have (perhaps including many science teachers) concerning the Creation/Evolution debate can be traced to a lack of understanding the distinction between these two sciences. Let’s begin with a basic definition of each and then observe how much this distinction affects our understanding of the issues.
Operational Science can be defined as any science that sets out to describe how something works. It uses the traditional tools of observation and experimentation. Examples of this sort of science would include physics and chemistry.
Historical Science can be defined as any science that attempts to piece together past events in order to explain those events. Examples of Historical Sciences would include Archaeology and Police Forensics.
A key difference between these two types of science is that theories in operational sciences can usually be thoroughly tested in order to prove whether or not the theory is true. In contrast, in historical science, theories generally cannot be tested and always have some level of assumptions and doubts.
All theories about the formation and creation of the universe, the world, life, and man fall into the category of historical science. The events are all past events that are not observable.
Often pro-evolution debaters will ridicule Creation by comparing it to a now debunked theory in the operational sciences. A common example of this is the theory that the earth is flat.  This is a false comparison because we can test to see if the earth is round or flat by flying into space and observing it, but we cannot observe the formation of the earth because that was a one time event in the past.
This does not mean that historical sciences are all bunk. Historical sciences do use scientific methods to try to understand past events, but it is critical to keep in mind that there are always assumptions built into these methods. If the assumptions are wrong, then the theory’s conclusions are probably wrong as well. For example, radiometric dating methods  are often used to date the age of rocks but all of these dating methods have two important assumptions – the amount of material being measured started with a particular amount when the rock was first formed and the rate of radioactive decay has always been the same. These are two very big assumptions that are virtually unknowable and yet these methods are used to “prove” the age of the rock. In actuality, they are not capable of proving anything because the underlying assumptions are un-provable.
Assumptions can be likened to faith. A creationist assumes (has faith) that God created the earth and an evolutionist assumes (has faith) that random chance created the earth. An assumption is a belief that is based on something that cannot be proved. Assumptions are used to help interpret facts that do not have a clear meaning. For example, evolutionists look at rock layers they find in the ground and because they assume, believe, or have faith in the idea that the earth is very, very old they interpret the fact that there are layers in the earth to mean that they were laid down over long periods of time. However, a creationist can take that same fact, that there are layers of rock in the earth, and because he or she assumes, believes, or has faith in the idea of a young earth can interpret the layers as being laid down quickly during the flood of Noah. However, if an assumption is wrong then the conclusion will most likely be wrong as well.
Assumptions are fundamental in Historical Sciences. Because a historical event cannot be recreated and observed, there will always be assumptions built into any theory about that historical event. Therefore we can see that in the Creation/Evolution debate nobody has proven anything about the origin of the earth, life, and man. There are basic assumptions being made on both sides of the argument which cannot be definitively proven.
So then, how do you know what is the truth when it comes to history? By testing the interpretations to see if they hold up. For example, most evolutionists believe that life evolves through a process of random genetic mutation and natural selection,  but after nearly a hundred years of breeding experiments to see if random genetic mutation (often sped up through the use of radiation) can produce new genetic information and subsequently new genetic features, testing has thoroughly shown that random genetic mutations do not produce new genetic information. As a Christian then, how do I test my assumptions about the Bible and what it has to say about the origin of life? There are certainly scientists doing research and experiments that give credence to the claims of the Bible but even as a Christian who is not a scientist I can test my assumptions about the Bible. By applying the Bible’s lessons in my life I can see whether or not the fruit promised in the Bible comes to pass, if it does then I have evidence that the Bible is true.
Understanding the difference between historical and operational science helps to clear up some of the confusion in the Creation/Evolution debate. The origin of life on earth and the origin of all species of animals and plants are historical events. They cannot be observed. Any conclusions we draw about how these events occurred will depend on assumptions that we must make. If our assumptions are wrong then our conclusions are wrong. The underlying assumption of Creation is that there is a God. The underlying assumption of Evolution is that there is no God. Which assumption do you believe?
 As an example of this, in October of 2005 a coalition of 70,000 Australian scientists and teachers made this claim in a letter of protest about the possibility of the teaching of intelligent design in the classroom. See http://www.smh.com.au/articles/2005/10/20/1129775902661.html?from=top5
 All radiometric dating methods use a process of measuring the amount of decay from an unstable material such as Uranium into a stable material such as Lead. In other words if I have 100 Uranium atoms and 100 Lead atoms in some material and the rate of decay for a Uranium atom into a Lead atom is 1 atom per year, then the material is 100 years old assuming that there was no Lead in the material to begin with. The actual process is more complicated than this but this gives the general idea.
 Natural Selection is the process by which living organisms that are more suitable to their environment have a better chance of reproducing and thus produce more offspring.