A professor’s take on laws, theories and cats

By Steve Humphrey
Illustration by Andrea Hutchinson

In my previous column, we explored the matter of logic versus rhetoric and how we can distinguish the two. Now, let me begin this month by distinguishing metaphysics from epistemology. Metaphysics is the study of what there is in the world – the furniture of reality, as it were. Epistemology is the investigation of what we can know about that world, and how we can gain that knowledge.

Science begins with the metaphysical assumption that a mind-independent, external, objective physical world exists and that we can gain knowledge about that world. This might seem obvious, but it has been challenged. There are those who believe that our experience of the external world is illusory – a shared hallucination like Neo in “The Matrix.”

So, if we grant the assumption that our experiences are of an external, objective reality, what constitutes “truth?” For starters, what sorts of things can be said to be true or false? Generally, it is believed that propositions, or declarative statements, have objective truth value. For example, questions and commands are neither true nor false. Now, what makes a proposition true? That is, what features of the physical world determine the truth value of some statement? Scientists believe the correspondence theory of truth, which holds that true propositions describe, or correspond to, facts in the world. According to this view, the proposition “the cat is on the mat” is true just in case the cat is on the mat. An alternative view might be that “the cat is on the mat” is true just in case everyone believes that the cat is on the mat. But for science, truth is not a function of opinion, intuition or consensus but of facts in the world.

There are general as well as singular propositions. A general proposition is one that makes a claim about multiple entities. “The cat is on the mat” is singular, “all cats love to sit on mats” is general. Science is primarily concerned with general statements. A collection of individual truths doesn’t tell us very much, but a true generalization tells us a great deal. It is shorthand for a huge conjunction of singular statements. The object of science is to find and characterize patterns and regularities in the physical world, and these are described using general propositions. These are called “hypotheses” or “theories.” In the physical sciences, such general claims are expressed in the language of mathematics in the form of equations. Such expressions are often called “laws,” as in “the laws of physics.” Laws simply describe patterns and regularities in the physical world, and they can be used to make predictions about future observations. The “truthmakers” of general propositions are general facts or collections of particular facts. General claims may be universal (“All cats like mats”) or statistical (“75 percent of cats like mats.”)

Some philosophers are of the opinion that laws exert some sort of force on the world – that they cause things or prevent things. I picture “cosmic cops” on cosmic Segways zooming around keeping things in order. For me, laws are simply descriptive, not prescriptive or proscriptive. That is, they tell us how things are, not how they should be or can’t be.

Next time, I will talk about what makes us think that some hypothesis is true and what justifies our belief in that proposition. V

Steve Humphrey has a Ph.D in the history and philosophy of science, with a specialty in philosophy of physics. He teaches courses in these subjects at the University of California, Santa Barbara, and has taught them at the University of Louisville.