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Evolution, Historical Methods, and Assumptions

Andrew Lamb has commented on a post I wrote back in July. I have responded to most of the comment there, but he references an article of his own, Immeasurable Age, and it employs an approach that, while I do not think it has merit, is so common in both public discourse and apologetics, that I want to respond.

In the comment he states:

Contrary to your assertion Henry, age is dependent upon assumptions, i.e. age is not something that can be measured. See the article Immeasurable age.

It’s interesting to note here that Mr. Lamb introduced the term “measured” and then uses a mildly eccentric definition of the term. Apparently if any form of inference is involved, one is not measuring. But we use various types of inference in a number of measurements. For example, inference is involved in measuring radio frequencies. One observes the effect and from there infers the frequency.

Now you should rightly point out that my example of inference is substantially different than the types of inference involved in determining the age of the earth. (Note again that I did not use the term “measure.”) That is why I called his use only mildly eccentric. There is no device, such as a time ruler that I can put up against the time line of earth’s history and read off the actual age. That is the nature of historical study, whether human history or historical science. (At the end of this post I will provide links to a couple of online sources on the age of the earth. I’m not planning on discussing the actual science, but rather the general approach.)

I would prefer better definition of terms like “assumptions” (which Mr. Lamb uses) or “presuppositions” (which is seen frequently elsewhere). In this case Mr. Lamb is using “assumption” in a manner that borrows some of the baggage of “presupposition” without actually going there. (A presupposition is something one must suppose or assume to be true to make sense of a worldview, i.e. it is unquestionable within that worldview. An assumption can be something that one takes temporarily to be true, but which one intends later to test–or not, as the case may be.)

Thus I would immediately disagree with the definition Mr. Lamb provides in his article:

All three methods involve making assumptions. Assumptions are things we believe, but which cannot be proven.

That definition is closer to the definition of a presupposition. Now note that I’m not much of a fan of the term “presupposition” either, but I’m much happier with it when it is either carefully defined by an author, or used in a standard defined sense. I have found so many senses of the term, however, that I think each author would do well to state how he understands the term whenever it is used.

A more serious problem, however, is the way that this idea is used in the article. We are told that because the age of the earth cannot be measured, but is rather based on assumptions, pretty much anything goes. Lamb gives a number of ideas of measuring age based on clearly false and ridiculous assumptions, such as checking your current rate of growth and extrapolating, thus implying without saying so that scientific assumptions (if such they are) are also perversely stupid. One could summarize this as “It’s all based on assumptions (probably bad ones), so why not ours?”

To quote:

When it comes to the age of the world, we can use historical methods (method 1 above), which involve assuming or trusting particular records to be accurate. This is the way we at CMI calculate the age of the earth. We trust the Bible to be a supremely reliable record of world history, and from the information in the Bible we can calculate that the world is about 6,000 years old.

So we are to believe that the assumption that the records in the Bible are accurate, and the assumption that rates of radioactive decay have remained essentially unchanged, are to be placed on the same level. Then if one is a Christian, of course one should accept whatever the Bible says over equally speculative scientific options.

I hope you note the way I worded that. I believe a number of my more conservative friends would be uncomfortable with the idea that the accuracy of Biblical records was simply one assumption among many, so hey, why not accept it.

But the assumptions involved are not even close to the same level. An age based on radioactive decay may be based on an assumption of a constant rate (though more on that later), but the assumption that the earth is 6,000 years old is based not on a single assumption, but rather on a large number of them.

  1. We assume the Bible’s accuracy
  2. We assume that the Bible intends to present us with history in specific passages
  3. We assume that we read those passages correctly
  4. We assume that genealogies are, or are even intended to be, complete
  5. We even make an assumption of constant rate in reading Genesis 1, that each day is 24 hours long even when it occurs before the appearance of the sun
  6. . . . and many more

But do we have to make such assumptions, or are these things testable? Other ancient records go well beyond the 6,000 year history based on the Bible. The great pyramid and the Sumerians, amongst others, would have live through the great flood. In later years, records from these other nations can be synchronized with part of the Biblical record. If we can synchronize the record at one point, why would we take the Bible in isolation earlier, unless it proved to be accurate in providing this specific type of historical data?

I discuss the issue of historicity in the Genesis accounts on my Participatory Bible Study Blog in articles Historicity of Genesis 1-11, Literary Types in Genesis 1-11, and Perspective on Vocabulary and Genre in Genesis 1-11. To summarize, there are good indications that these chapters are not intended as narrative history, and if they are not narrative history, then the assumption (!) that one can glean that type of information from them would be incorrect.

But my intent here is not to prove the 6,000 year old earth wrong. While I avoid the term “prove,” I think that the evidence against a young earth is so strong that it is perverse to reject it. But what I am concerned with here is what one does with the concept of “truth.” This isn’t capital T “Truth” with which one can pound the table, but valid data on which one can base sound decisions for one’s life.

I depend on such information from science and technology all the time as I live my life. I’m using a computer that is based on such information. Of course, I am again not speaking of historical information.

So let’s turn to the resurrection. I’ve discussed recently how far from proof this is, and looked at a couple of attempts to place it on firmer ground. Some of my conservative friends may be concerned that I’ve given away the store by stating that a miracle can’t be the most probable explanation of an event by nature from an historical point of view.

But one can provide some evidence that sets up the circumstances and the results of the resurrection. This too is based on many assumptions. First, one assumes that there were witnesses, that nobody just made this all up. Second, one assumes that this material was passed on with any sense of accuracy. Both of these assumptions involve a set of other assumptions about the nature of the ancient world and how its people worked.

But if I use the word “assumption” in the manner in which Mr. Lamb uses it, I would say, “Well, those are your assumptions, and that’s how you choose to believe.” There’s no basis for testing and discussion. Any believe is equally plausible because they are all based on assumptions. But are all assumptions equal?

What I would suggest rather, is that each of those assumptions can be discussed and tested and we can discover what is more or less probable. Then we can build a complete picture based on the best set of parameters we can work out. Note that I begin to deviate seriously here from the definition of “assumption” that I stated earlier. That’s because I believe it is the wrong concept to use.

“It’s all based on your assumptions” parallels “that’s just your interpretation” in terms of tearing down the possibility of intelligent discourse and discovering truth. “That’s just your interpretation” suggests that a text actually has no meaning of its own, and anyone can read into it whatever they desire with equal validity. “It’s all based on your assumptions” does the same thing to scientific data.

As used here, some “assumptions” are more equal than others, with apologies to George Orwell. Only in this case I’ve inverted the idea, and it is true and right that some assumptions be more equal.

In fighting what he perceives as falsehood, Mr. Lamb has taken an unwitting (I hope) shot at any sort of truth or validity.

To simply consider one thing regarding the age of the earth, one of the most common young earth creationist objections to constant rate in a natural process is the idea that the global flood would have massively changed deposition rates, as indeed it would. But the first point here is that there is no assumption that deposition rates everywhere and at all times are the same, but rather than the physical laws that govern them remain the same.

Scientists are well aware that a flood deposits different things at different rates depending on the specific conditions. That’s why they can look at the state of the geologic column and be quite certain that there was no global flood. It would have left certain depositions. Old earth creationists are willing to go with the evidence here and understand the flood to be more local, though certainly great enough to stand out.

Amongst the things that one can use to check deposition are the fossils of creatures that lived at that time. For example, if a layer was deposited instantly in a massive flood, all of the creatures involved would have to have been alive at one time.

Just as we can divide up the various assumptions that we would have to make about the Bible in order to get the young earth position, we can divide up the assumptions here as well. Then we can test these one against another. One need not make all these assumptions at once, and many of them can be tested and determined to be probable or improbable.

Let me provide references to a couple of articles:

Abundant Evidence, Skepticism, Apparent Age (from the American Scientific Affiliation). Provides a more detailed discussion of the relativism involved in this type of argument.

FAQ: Age of the Earth (Talk.Origins Archive). Goes into more of the nuts and bolts.

CB102: Mutations Adding Information (Talk.Origins Archive). A good starting point on this issue, raised in Mr. Lamb’s comment to the earlier post.

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  1. Martin LaBar says:

    Your usual good job. I like, especially, your distinction between assumptions and presuppositions.

  2. Laura says:

    I really enjoyed this, and I don’t like delving into the topic, as you know. Now I just have to find the time to work through those links. 🙂

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