In this article we shall discuss the concept of actualism and some common misconceptions which surround it.
What is actualism and why?
Actualism in geology is the idea that the facts of geology can and should be explained in terms of the sort of physical processes that actually happen.
As such, it can be considered both as a scientific theory (that the facts can be explained by real processes) and as a methodological principle (that they should be so explained).
You might wonder why there is a need to have a name for this. You might also wonder why it is necessary to mention it particularly in a textbook on geology, since after all this is a universal scientific principle. Chemists (to take one example) are just as much actualists as geologists, because all scientists are; and yet they do not include a section on actualism in their textbooks.
The reason why it is mentioned particularly in geological textbooks is a historical one. For many centuries people have been trying to explain geology in terms of non-actual, magical processes: explaining, for example, that the Earth's strata were produced by God turning off the force of gravity and then turning it back on; or that God created fossils when he made the Earth so that coal-miners even when underground would have visible signs of his presence. Various religious sects still promote non-actual concepts of geology to this present day.
Actualism as a theory
As we have said, actualism (considered as the assertion that the geological record can be explained in terms of real processes) should be regarded as a scientific theory. Why? — because it is testable. We can look at the rocks, and we would recognize if there was something in the geological record which could not be explained in terms of real processes.
In fact, as you will recall from previous articles, what we find is that we can explain what we see: we can explain glacial till in terms of glaciers, marine limestone in terms of the deposition of calcareous ooze, chemical weathering in terms of chemistry, paleomagnetism in terms of continental drift, saline giants in terms of the evaporation of seawater, and so forth.
If there are still things that are not yet perfectly explained, such as the question of how exactly glaciers make drumlins, then we can hardly regard that as a falsification of the theory, but merely an area in which more work needs to be done, for it is not plain that drumlins cannot be explained by a better understanding of actual glacial processes and would instead require the invocation of a non-actualistic being such as the Drumlin Fairy to fill this minor gap in our knowledge.
If, on the other hand (for example) we split open two leaves of slate and found therein the first chapter of Genesis written in quartz, then this would falsify actualism; we could not even imagine that one day we would find any ordinary physical process that would explain the phenomenon: we know too much about the way in which the world works to consider that even for a moment.
Actualism as a methodological principle
Considered as a methodological principle, actualism may be stated in the phrase: "If it looks like a duck and it quacks like a duck, it's a duck".
Take aeolian sandstone, for example. It looks exactly like lithified aeolian sand; we can understand it perfectly well in those terms. Therefore, this is the most parsimonious way to understand it: it is simply unnecessary to imagine an unknown unobserved process to explain what can be explained by a known observable process.
Now, there are some people who (for religious reasons) dislike this: they wish, for example, that aeolian sandstone was something else altogether. These people, let us hasten to say, are perfectly entitled to their own beliefs. But they are not entitled to pass such beliefs off as scientific: when they daydream about alternative magical processes that might have formed something that looks exactly like lithified aeolian sand formed by actual processes, they have abandoned the scientific method in favor of wishful thinking.
For the proposition: "If it looks like a duck and it quacks like a duck, it's a duck" stands at the heart of all scientific thought. We may imagine that it is not a duck; we may imagine that it is in fact a magical fairy disguised as a duck. It is in a sense as easy to imagine this as that it is a duck, for the human imagination is not constrained by actualism. But the scientific method is constrained by actualism: within that method we cannot put the fairy hypothesis ahead of the duck theory, we cannot even place them on the same level. The idea that it is a duck is to be preferred for all scientific purposes unless and until we find evidence that it's a magic fairy. Those who prefer to think otherwise have not merely stepped outside the edifice of the scientific method, they are throwing bricks through its windows.
We should note that the adoption of actualism is not the same as the adoption of philosophical naturalism (the rejection of the existence of processes other than the physical). Supernatural beings and processes may perfectly well exist; it is no function of this textbook to pronounce on such a question. It is simply that we can see no evidence in the geological record that such processes have ever been involved in geology; hence actualism succeeds as a theory, as I have explained.
And, that being so, we are obliged to uphold it as a methodological principle. In the words of William of Conches: "God can make a cow out of a tree, but has He ever done so? Therefore show some reason why a thing is so, or cease to hold that it is so." Let us concede that God can make a cow out of a tree; but unless we have a reason to think that he has done so, we must explain the historical origins of any particular cow as involving a mommy cow and a daddy cow; there is nothing to justify the idea that God made the cow out of a tree even once we have admitted his power to do so if he really wanted.
The view which we have called "actualism" is sometimes (perhaps more commonly) known as uniformitarianism.
However, this word is often misleading. As a term in the history of science, it often refers to ideas some of which no living geologist considers to be true. And as a term in religious apologetics, it often refers to ideas which no geologist in the entire history of geology has ever considered to be true.
For that reason, in this text I have thought it best to retire the old word and go with the more modern term "actualism" instead.
The term "uniformitarianism" is misleading in itself: for when modern geologists call themselves uniformitarians, what are they claiming to be uniform? No less than the laws of nature themselves — but not necessarily anything else. Every geologist will insist that many things have not been uniform over the course of the Earth's history: its flora and fauna, for example, have not stayed the same; its temperature has not stayed the same; the composition of its atmosphere has not stayed the same; the arrangement of continents has not stayed the same; the global climate has not stayed the same.
What has apparently stayed the same is that throughout all this change the laws of nature have been uniformly unbroken, and only actual processes have taken place. In modern parlance, a "uniformitarian" geologist asserts no more than that; he or she has no general belief in uniformity, merely in actualism.