Necessity, Sufficiency, and Evaluating Claims

Many people are confused about the difference between necessary and sufficient conditions or causes, and the confusion leads to a tendency to make exceedingly awful mistakes in evaluating claims.

This post examines the difference between these concepts and explains how to use them in drawing careful conclusions about the universe.

Read on for more.

A necessary condition or cause is – exactly as the name implies – something needed to produce a certain result or outcome. The outcome can’t be produced without a necessary condition, but the necessary condition, all by itself, won’t produce that outcome.

For example, if someone wanted to light a barbeque grill, a necessary condition is the presence of some kind of fuel (usually from a propane tank purchased at the beginning of barbeque season). But all by itself, the presence of fuel isn’t sufficient to light the grill.

A sufficient condition or cause is – again, exactly as the name implies – something that brings about a given outcome (but is not necessarily needed to produce the outcome in all situations).

So, for example, a lit match thrown into a grill (the valve of whose propane tank has been opened, of course) is sufficient to cause the result. At the same time, a match isn’t always necessary – one could use one of those long lighters to ignite the barbeque. Heck, a lightning bolt striking a grill just right might be sufficient to light it (but certainly not necessary).

So far so clear? It’s not exactly a difficult concept to grasp, but putting the concepts into practice is considerably harder for a lot of people.

A number of religious believers, for example, argue that their God must be real because he is a sufficient explanation for the universe. The universe needs a creator, they say, and God is defined as having universe-creating powers, so it makes sense to say that it’s likely that God (or some conscious being like a god, with universe-creating powers) produced the universe.

Indeed, a magical being with universe-creating powers would be sufficient to explain the existence of the universe…but the problem is that nothing suggests that such a being is necessary. Perhaps some other sufficient cause is responsible for the existence of the universe, including some kind of completely natural force.

I used a similar example on this blog recently when I gave the hypothetical situation of a man who has lost his keys and who claims that aliens must have taken them. Indeed, aliens taking one’s keys would be a sufficient explanation, but it’s not necessary, and nothing suggests that it’s necessary in this particular case.

A similar example was recently explored on a weird thread on Lashtal.com, where a poster proposed that God (unbelievably, he wanted to use the God of Christianity as an example for some reason) can be said to influence energy (and therefore, presumably, would be responsible for all of the physical “laws of the universe”).

Again, a God directing physical energy would be a sufficient explanation for the “laws” of physics, but it’s not a necessary explanation. It might be, for example, that matter simply behaves in certain regular ways, without any conscious interference of any being. The “laws” of the universe, after all, are not proscriptive the way that human laws are (molecules don’t get to “choose” to obey the law or face an authority that can give them tickets, for example): they are descriptive. They describe the ways that matter acts, and matter seems to act in regular, blind ways, undirected by any agency.

In other words, we observe a phenomenon (matter acting in regular ways). We all agree that matter acts in certain ways. Person X proposes it acts this way because some “God” directs it. Person Y proposes it acts this way because magical pixies direct it. Person Z proposes it acts this way because “all is consciousness” and the conscious nature of the universe determines how it will act.

All of these explanations are sufficient, but in the absence of any evidence that suggests that any one of them is necessary, they are all superfluous. Parsimony – not to mention our desire not to fool ourselves into accepting random, bullshit ideas – requires that we discard these unnecessary assumptions and just stick with the original point, the one we all agree with (that matter acts in regular ways). Matter does act in regular ways, and – without any grounds for saying that anything else is necessarily going on – we have no grounds for accepting any extra claims about matter.

The examples given above all deal with people proposing sufficient solutions without being able to demonstrate that they are necessary. Let’s consider the opposite situation: someone realizing that a condition is necessary but confusing it with a sufficient condition.

An example of this can be seen  on The Thelemic Fruitcake Factory, where the poster “Bereshith” – the confused kid who posted a comment to one of my previous entries and then ran away when he couldn’t address my argument – continues to misunderstand the concepts under discussion.

He writes in a recent thread that atheism is a kind of “belief,” supporting this claim with a ham-fisted insinuation that an atheist poster’s mockery toward religion must be motivated by (atheistic) belief. Imitating me, he asks, “"Logically, how can animosity be the result of a LACK of belief in something? It can't be, can it?" thereby implying that atheism must a be a belief in order to be the motivation of animosity or mockery.

He still doesn’t grasp the relationship of non-belief to emotions and action because he confuses its necessity with its sufficiency in certain situations.

Take, for instance, hatred of religious belief. We might agree that non-belief (in a particular religious claim under discussion) is a necessary condition of hating that belief.

[One might object to this point on the grounds that there are plenty of cases of confused kids who “hate” the religion in which they were raised while still believing that the claims of that religion are true. There are also plenty of cases where someone can sincerely hold a belief and still poke fun at that belief or mock it. For the sake of simplicity, let’s discount those cases and assume that not holding a belief is, at least most of the time, necessary to hate that belief]

Here’s the million dollar question, though: even though not-holding-a-belief is usually a necessary condition of hating that belief…is not-holding-that-belief, in and of itself, sufficient to produce hatred of that belief?

The answer is “of course not,” in the same exact way that the presence of fuel is a necessary condition to light a barbeque but isn’t, by itself, sufficient to get the fire going.

What could be the cause of someone hating a belief? Lots of things…a bad experience with someone who holds a particular belief, a dislike of the effects of that particular belief, a dislike of the poor reasoning that supports that particular belief, etc., etc., etc. Lots of things might be causes of someone hating a belief, and – in a given situation – they might even be considered sufficient, but one thing that can never (logically) be sufficient is not-holding-that belief.

This, by the way, is the exact reason that I pointed to – in my other post on the subject – the fact that non-believers are often indifferent to religion or even friendly to it. In and of itself, not-holding-a-belief can’t cause someone to hate that belief, even if it might be considered to be (usually) a necessary condition or at least consistent with that hatred.

Contrast that argument with, say, the argument that beliefs can cause action. To use the Salem Witch trials as an example, belief that there are witches and that it is good to execute them is sufficient to cause one to support publicly executing people as “witches.” Similarly, belief that the Pope is the infallible representative of God and that he should be obeyed is sufficient to cause one to go on the Crusades. Strictly speaking, these beliefs may not be necessary conditions (since one might want to do these things for other reasons), but in practice, they are usually necessary, too (Protestants and people who don’t believe in witches, for example, are hardly ever found engaging in Crusades or witch trials, respectively).

To give one more example of a sloppy use of causality, following the recent, disgusting school shooting in Connecticut, a number of ghoulish monsters – like Mike Huckabee, for example -- emerged from the woodwork to blame the violence on the fact that prayer has been removed from public schools in America.

First of all, this argument grossly misunderstands the situation in American public schools. No one “removed prayer” from schools…any student can pray at any time (as long as it doesn’t disrupt other students) and can pray silently in his or her head all day long. Furthermore, students can meet in Bible study groups after school and similar clubs. The only thing that has changed in American public schools is that there is no longer instructor-led prayer. School instructors, as representatives of the state in their capacity as public educators, are not allowed to lead students in formal prayer.

But even assuming that “prayer has been removed from public schools” is an accurate summary of the situation, someone making this dumbass argument doesn’t understand the way that causality works.

A lack-of-prayer in schools is neither necessary nor sufficient to cause an atrocity like the one that happened in Connecticut. Of course, a lack-of-prayers is consistent with a shooting (in that there are no logical contradictions), just as a presence-of-prayers is consistent with a shooting (in that there are no logical contradictions). But there doesn’t appear to be a causal relationship between the presence of prayer and the presence of violence. Of course, that doesn’t stop people who are confused about necessity and sufficiency from advancing these kinds of mind-numblingly stupid arguments.

People who want to have a clear picture of the world – and who want to avoid bullshitting themselves when at all possible – have a responsibility to evaluate their beliefs about reality and examine them with more depth and nuance than is typically done.