Sunday, February 27, 2005

The Force of Habit, part I

I know a nifty little trick for getting the ketchup (or catsup if we want to be pretentious) out of its bottle. Most people upend the bottle and try to pound it from the back. This doesn’t work very well because the ketchup forms a plug in the neck of the bottle due to the ketchup’s viscosity. The only way for the liquid to flow is for air to enter the bottle but the neck is purposely designed to restrict the flow of air in order to make the ketchup seem “thicker”. Pounding the back of the bottle can force some of the ketchup out by overcoming the viscosity of the ketchup by the direct application of kinetic force but this tends to result in splatter and it’s not much more efficient then simply waiting for the air to slowly bubble up through the neck.

A better way to achieve this is to hold the bottle at a shallow angle above the plate and to sharply tap the bottle on the neck perpendicular to the axis of the bottle. This forces the ketchup against the opposite side of the neck, allowing air to flow past the gap. Not only doesn’t the ketchup splatter but once it starts to flow it tends to continue flowing reducing the effort it takes to get it out while simultaneously making it pour at a reasonable rate. Give it a try and see for yourself.

I’ve shown this trick to quite a few people over the years. The curious thing, though, is that, of all the people I’ve shown this little technique too, not a single one, to the best of my knowledge, has adopted it. They continue pounding the backs of their bottles, or digging the ketchup out with a knife, or simply waiting for the ketchup with a stoic patience. I’ve often wondered why no one chooses to adopt a method that is clearly superior to what they’ve been doing. Over the years I’ve come to the conclusion that the answer is habit. People pick up a certain method of getting the ketchup out of the bottle at a fairly early age and become so accustomed to it that they can’t change — can’t even think to change — even when a better way is demonstrated to them.

Habits are powerful things. Some habits are good, like brushing one’s teeth after ever meal, some are bad, like picking one’s nose, but they all exert a compelling force that makes it difficult to break them. In fact, we have a special term to describe adverse habits that are nearly impossible to break by force of will: addictions. It takes no act of genius to see that habits are an important part of human behavior and that we can’t really understand why we act as we do unless we factor them into our considerations, but are habits powerful enough to explain all of our actions? Are they, in fact, required to explain why we act as though we live in a universe that is consistent and predictable? Hume thought so.

In order to understand why Hume thought this, it’s necessary to understand a bit about induction which, in turn, requires us to know a bit about logic, which requires us to know a bit about epistemology which, finally, requires us to understand something about philosophy in general. Don’t worry, unlike my last epic, this won’t take too long (I’ll be done next week — I promise!)

When you bring up the subject of philosophy, a lot of people immediately roll their eyes. To them, philosophy is nothing more or less than a bunch of ever-educated snobs splitting endless semantic hairs. To be fair, there is a lot to that stereotype. Much of what goes on in academic circles is tantamount to quibbling over definitions (although such quibbles often do have a point and a purpose) and much of what passes for deep contemplation is more than a little silly (I’ll save that discussion for when I’m in the mood to tackle postmodernism); however, the basic goal of philosophy is, I believe, worthwhile. That goal is nothing less than an attempt to pursue truth. That can be truth with a small T, meaning the pursuit of facts about the universe and certain abstracts such as justice and ethics, or it can be Truth with a big-T, meaning that which is absolute, eternal and immutable, qualities that have led some theologians to identify Truth as being synonymous with God (and lest you be tempted to pedantics, theologians are typically concerned with God and not gods but, again, that’s a topic for another time). In this essay, we’re going to be concerned with the former kind of truth.

Philosophy has two grand divisions (and various lesser ones). One division, ontology, deals with question of existence. One often finds ontologists talking about the nature of existence and asking questions about the essence of entities. The other division, which will concern us, is epistemology. The subject of epistemology is knowledge. Many of us are familiar with Descartes’ demon where Descartes posited the existence of an infinitely powerful deceiver. He asked himself what we can know given the possibility that such a deceiver exists. Descartes conclusion was that the only thing we could know was our own existence: cogito ergo sum. This is an example of an epistemological reduction, but let's not get too sidetracked.

Most philosophers believe that knowledge isn’t quite so elusive, although it is worth noting that it’s difficult to even devise a good definition of knowledge. Epistemologists contrast knowledge with belief. Beliefs are propositions that individuals hold to be true. A given belief may or may not, of course, be true. Knowledge represents a particular category of belief. It is not sufficient that one holds a true belief in order for one to have knowledge. If I believe that the planets trace out elliptical orbits around the sun because they are being tugged by invisible space elephants, my belief that the planetary orbits are elliptical is true but is, never the less, based on an ignorant belief (elephants, etc). Likewise, if I happen to accurately guess next week's lottery numbers, my guess does not indicate a state of knowledge (assuming, of course, that I’m not psychic) no matter how firmly I am convinced of its truth beforehand. One of Plato’s great contributions to philosophy was giving us a definition of knowledge that has held up fairly well for over two millennia. His definition is that knowledge is a state of true, justified belief. Of course that leaves us with the question of what constitutes justification. A general rule of thumb that I like is that one is justified in one’s beliefs if one could convince an unbiased, rational agent that your beliefs are merited. Even this can be challenging as evidenced by the so-called Gettier counterexamples which explore the question of accidental knowledge.

Leaving aside the thorny question of how we should define knowledge, epistemology also concerns itself with the generation of knowledge. How do we go about discovering truths? This is where logic enters the picture. I think the best way to think of logic is that it’s a kind of truth mill. At one end of the mill, you put in propositions which are considered to be true, you crank the handle and, from the other end, pop out new truths. The field of logic has a number of different mills to choose from. Most people have encountered the syllogism mill:

All men are mortal
Socrates is a man
Therefore, Socrates is mortal.

A syllogism consists of a major premise, a minor premise and a necessary conclusion, which is to say that, if we accept both premises, we are rationally constrained to accept the conclusion. As such, syllogisms are an early form of logic known as deductive logic. The hallmark of deduction is that their conclusions necessarily follow from the arguments (or premises) that lead up to them. In this respect, logical deduction is very much like a mathematical proof (indeed, many argue that deduction is properly a type of mathematics).

Deduction is a strong form of reasoning. It has two primary limitations, however. The first limitation is that a deductive argument is only as good as its premises. By example, you will sometimes hear it said that it is impossible to prove or disprove the existence of God. Strictly speaking, this isn’t true. There are dozens of logically consistent deductive proofs for the existence of God. There are also dozens of equally consistent proofs that God does not exist. Clearly both sets of arguments can’t be true but deduction isn’t, strictly speaking, about determining truth, it’s about making conclusions that are true if the premises that lead up to those conclusions are true. This is, obviously, a major caveat. If I start with the major premise that all dogs are gods and follow it with the minor premise that all gods must be worshipped then I can logically conclude that all dogs must be worshipped. Somehow I don't see many people accepting either the major or minor premise. Unfortunately, a logical argument can’t be used to establish the validity of its own premises (such attempts represent the fallacy of circular reasoning). Logicians try to get around this by limiting their predicates to “universally accepted truths”. When it comes to addressing important questions, though, such universal acceptance is difficult to come by.

A more subtle limitation of deduction concerns the sorts of truths that you can reach using it. As noted, the conclusion of a logical argument flows directly and necessarily from its arguments. If you think about this a bit it should be clear that this means that any truth you reach via deduction was already present in its premises. As such, deduction is less about generating truths than clarifying things which have been agreed to be truth. Such clarifications can be useful (we wouldn’t knock the Pythagorean theorem by complaining that it’s already contained in Euclid’s axioms) but it doesn’t really satisfy the primary goal of logic which is the generation (or discovery, if you prefer) of new truths. Enter induction.

Next week, I’ll detail what inductive logic is all about, why Hume had a problem with it, and argue that our reliance on it is rational in spite of Hume’s convictions to the contrary.

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