Has modern physics made logic obsolete? Does reality negate the rules of logic? I’m finding these questions or their affirmations becoming more and more common. While I was on vacation I read Steven James’ forthcoming novel Placebo. It was a brilliant, thrilling, and intelligent novel laced with elements from quantum physics. At one point we read, “Cyrus was a man of science, but if there was one thing quantum physics was teaching us, it was this: There is not always a scientific explanation for what happens in the world. Logic evaporates when you reach the subatomic level. Reality is much more malleable than it seems.” (223) Here I think he using “scientific explanation” as a synonym for logic since it is the science of physics that is evaporating logic. Now I would never suggest for someone to get their understanding of physics from a novel but I think it shows that some of the theories of physics are seeping into a lay friendly format. So let’s leave fiction and consider this paragraph from an essay by Andrew Davison called “Christian Reason and Christian Community” in Imaginative Apologetics edited by Andrew Davison (Baker Academic). (Davison is responding to Scott Hahn’s book Reasons to Believe.)
“Here we are presented with four supposedly universal principles of reason. Hahn claims that they are shared by everyone, independent of their religious position. This is an odd claim to make at the beginning of the twenty-first century. Fully respectable branches of mathematics, for instance, deny the principle of non-contradiction, as do various sorts of postmodern philosophy. Science and philosophy of all sorts qualify the reliability of sense perception, confirming a point already made in this essay: perceiving is already a work of interpretation; we have no access to ‘reality’ in an uninterpreted state. The principle of causality, as Hahn calls it, is particularly frowned upon today in philosophical circles. The populace at large may still think in terms of causation, but academics have been trying their best to invalidate the category of ‘cause’ for centuries.” (Bold mine for emphasis. 19-20)
While mathematics may be comfortable in denying the principle of non-contradiction it is hard to imagine that this same denial will carry over into the realm of reality and while academics may have been trying their best to invalidate the category of “cause” I’m not sure any could have been said to have been successful.
Recently this question came up in William Lane Craig’s Question of the Week. The questioner states:
But I think you are relying on commonsense and intuition too much in this day and age. We are not in an age where we can be confident that the laws of reason are the same as the laws of reality, like people in the time of Aristotle believed. . . . These examples should be an indicator that we shouldn’t really pursue our intuitions to their logical conclusions beyond the limits of the natural world. Because reason wants to follow the train of thought to the end, but apparently it is trying to deal with a realm that doesn’t work in human logic after a point.
Are the laws of reason and the laws of reality the same, as people in Aristotle’s time believed? Nothing has happened since the time of Aristotle that has undermined the truths of logic or logic’s applicability to the world. Aristotle’s logic is called syllogistic logic. He identified valid argument forms which are still recognized today, e.g., All As are Bs; no Bs are Cs; therefore, no As are Cs. This is an undeniably valid pattern of reasoning. The principal advance of modern logic over Aristotle’s is that modern logicians came to realize that the premises of syllogistic reasoning like “All As are Bs” have themselves a logical structure which Aristotle’s logic failed to disclose. A statement like “All As are Bs” has in modern sentential logic (the logic of sentences) the structure of a conditional: “For any item x, if x is an A, then x is a B.” This allows us to make inferences that Aristotle’s syllogistic logic cannot express, e.g., “Whatever begins to exist has a cause; the universe began to exist; therefore, the universe has a cause.”
Formal logic has become a discipline of incredible technical precision and rigor, akin to mathematics. Indeed, formal logic often goes by the name mathematical logic. There is nothing in the advance of this discipline that should lead us to doubt reason’s ability to make valid inferences about reality. Indeed, the development of subdisciplines like modal logic (the logic dealing with the necessary and the possible) and counterfactual logic (dealing with subjunctive conditional statements) has been a great asset in our being able to reason more carefully and rigorously when doing metaphysics.
Don’t confuse Aristotelian logic with Aristotle’s physics! Aristotle was not only a great philosopher but a natural scientist as well. As you might expect, his scientific work has been superseded by subsequent science, as more sophisticated instruments for probing the physical world have developed. As science advanced in our understanding of nature’s laws, Aristotelian physics was replaced by Newtonian physics, which was in turn replaced by Einstein’s physics, which will soon, we expect, be superseded by a quantum gravitational unified physics. In each successive scientific revolution, the earlier science is not simply abandoned; rather its truths are recast and preserved in the theory that supersedes it and its inaccuracies abandoned.
I hope you can see that none of this gives any cause to doubt the efficacy of human reason in knowing reality; quite the contrary, this is testimony to the incredible power of human reason!
You can find the complete Question and Craig’s response here. I find Craig’s response persuasive.