There are some people who say that science cannot tell us about what happened in the past. They say that science must be about verifiable or repeatable things. And since we cannot observe first-hand what happened in the past, those things lie outside of the scope of science—or so the argument goes.
To be honest, it would be absolutely crippling to science if it were prohibited from making claims about the past. Just imagine, for example, if physicists weren't allowed to speak about what happened three minutes ago inside their experimental apparatus. And why, if it is acceptable to speak about three minutes in the past, would it not also be acceptable to talk about thirty minutes in the past, or thirty years, or thirty million years?
Granted, there are some aspects of past events which are omitted from our best scientific descriptions of those events—not because those events are in the past, but because the sciences employ a strategy of abstraction. For example, physics paints a highly accurate picture of what happened at the beginning of the universe, i.e. at the Big Bang. And yet, the physicist’s picture of the Big Bang is an abstraction. The physicist’s picture stands to the actual Big Bang as an anatomist’s drawing stands to an actual human body: the drawing may be “true”, but it omits many important features of the actual, flesh and blood person.
We'll return to this issue below, but let's begin with a simpler question: Is it possible to know things about the past?
Some extreme empiricist philosophers, such as David Hume, have said that we can’t. But that view really is extreme–so extreme that it would be crippling to human action. Most of us assume that we know many things about the past. For example, I know what I ate for breakfast this morning. I also know that I have been alive for over four decades, and that about ten seconds ago I typed the word "know.” So, it's pretty safe to say that we can know some things about the past.
Besides the mundane events of our own lives, it also seems possible to know some things from the more distant past. For example, I know that in the middle of the 20th century, there was a war that ravaged the continent of Europe. I also know that many people were killed in concentration camps during this war. We can know these things because we have evidence about what happened, either through eyewitness testimony, or through other markers that were left by those events. For example, we can find evidence that the US dropped an atomic bomb in 1945 by traveling to Hiroshima and looking at the scorch marks on some of the buildings.
There seems no limit to how far back into the past we can push our knowledge. Just as there is good evidence that the holocaust occurred, there is also good evidence that Julius Caesar crossed the Rubicon. Pushing even further into the past, there is good evidence that human beings once lived side-by-side with Neanderthals. And many of us believe that there is good evidence that the universe is an astounding thirteen billion years old.
Perhaps you disagree with some of science’s claims about the distant past. That's OK. So far I have only argued for the more modest claim that we can know some things about the past. If you agree with that, then we can move on to the question of whether science is permitted to speak about the past.
That's still not a great question, because it's phrased in a way that makes "science" seem like a person. Science doesn't "speak", or do anything else. It is we, human beings, who engage in an activity that is called science. So a better question is: when we're doing science, should we ever try to say anything about the past? Or, more specifically, should we believe scientific theories that say things about the past?
Now we see that the question is about our own objectives. We human beings are captains of the ship called "science," and we choose where we want it to go. The question is: do we want to take it to distant places and times?
In order to answer that question, I think we need to ask ourselves again what we are hoping to accomplish by doing science.
Some people say that the goal of science is to gain knowledge. But that's far too broad of a goal. We can gain knowledge in a lot of different ways, many of which wouldn't really count as science.
What seems to make science special, as a method of seeking knowledge, is that it's systematic and that it looks for patterns. From a Christian point of view, we can think of science as an attempt to reconstruct the blueprint for part of God's creation.
From that point of view, there seems to be little doubt that science could be a great aid for understanding the past. The past, present, and future are all part of God's creation. Creation is like a huge mansion, built on a common plan. When we're doing science, we're hoping to sketch this plan. And if we're successful, then our sketch will illuminate not only the present and the future, but also the past.
But notice that this picture of science–as "reverse architecture"–has limited aspirations. We don't say that science ought to uncover all truths, or that science is the only method for gaining knowledge. Science provides a specific type of knowledge of the structure of creation.
Christians believe some things that lie outside the domain of direct scientific inquiry. In particular, Christians believe that God has, on occasion, acted decisively to move redemptive history forward. The reason we believe this is not because of some scientific evidence, but because God spoke through the prophets and finally through Jesus Christ. We don’t think the significance of those events can be distilled from looking at the “pattern of creation.” These events are described to us as brought about directly by God, and so we shouldn’t expect them to show up on the blueprint for creation.
There is a further reason why science doesn’t say everything about the past: past events are highly specific and contingent, whereas science aims to find patterns, generalities, and regularities. It is a virtue of a scientific theory to be general rather than specific–and thus to omit mention of specific people, places, or things. Just look at a typical science textbook–say a book on Einstein’s general theory of relativity. That book won’t say anything about specific individuals such as George Washington, or about specific places such as Grand Rapids, Michigan, or about specific times such as 8:17am on December 2nd, 2007. That textbook probably won’t even mention the planet earth, except possibly as an example of one (non-specific) massive object orbiting around another (non-specific) massive object. Science textbooks present us with theories which should be applicable to a wide variety of situations, but which cannot tell us everything about any particular situation.
For example, consider a historical event like Caesar crossing the Rubicon. That event occurred once – in a specific time, at a specific place, and it involved specific individuals. Because that event is singular, there is no scientific theory that purports to say everything about it.
There are sciences that say many interesting things about the past. For example, physics says that our universe was initially in a hot dense state and that it has been expanding for billions of years. Similarly, evolutionary biology says that the current configuration of animal species is the result of descent from a single common ancestor. The actual, concrete history of our universe includes many highly specific facts that science hasn’t explained, and that it may never explain. But science does aim to describe general patterns that were exemplified in the past, and which may still be exemplified today.