Bitbutter

David Hume pointed out that inductive inferences are not rational, but arise from custom and habit. One way to illustrate this is to think of whether the sun will rise tomorrow. Most of us will agree that the sun is more likely to rise tomorrow than it is not to rise.

But which ever way we explain our judgment about the likelihood of a sunrise, all our explanations depend on the assumption that the future will resemble the past in a fundamental way. To give a more concrete example: We assume that the laws of physics we understand today won't be radically contradicted by how things behave tomorrow.

But what are these assumptions based on? How can we know that the laws of physics that explain the earth's rotation will still hold tomorrow? It seems that we can't claim to know these things, and it's not immediately obvious how we can even assign probabilities to them.

It can feel unsatisfying to think that our expectations about the future are inherently irrational. The presuppositionalist thinks that he has a way out. He believes that a god exists who has promised to maintain the uniformity of nature. We can take the the uniformity of nature to mean that the future will resembling the past in some fundamental way.

There are at least two distinct kinds of problem with this 'solution' though, either of which invalidate it. They can be summarised as follows:

1. We can't trust a god's promise without using induction. So if you're using God's word to justify induction, you're begging the question.

2. Even if nature is uniform, this isn't enough to provide a rational justification for induction, as illustrated by the black swan example.

How to trust God's promise?

According to the presuppositionalist, God has promised to maintain the uniformity of nature, which is needed if inductive inferences are ever going to turn out to be true.

God is all powerful and his word is final so that might seem to settle things. But even if we ignore the so-called biblical evidence which plainly shows that god often changes his mind and breaks his promises, it's not as simple as that.

How do we know to trust someone's promise? In deciding about their trustworthiness we take things into consideration about the one who's making the promise: a particularly important consideration is whether the promise-maker has broken or kept his promises in the past.

To see that this applies even if we're considering a divine promise-maker, think about how you'd react to a new promise from a god who'd made many promises in the past, and broken all of them; even his most devout worshiper would be a fool to trust him.

So the presuppositionalist uses the ideas he has about how his god behaved in the past and comes to the conclusion that god is very unlikely to break his promise about the uniformity of nature in the future. He's using induction.

God never lied to me in the past, therefore God won't lie to me in the future.

But remember that induction is the very thing the presuppositionalist wanted to justify in the first place. The presuppositionalist might protest that he's not really using induction to know that god won't lie. He might say that he knows God won't lie because it's not in God's nature to lie. But all he's done is generate a different inductive equation:

God's nature was X in the past therefore God's nature will be X in the future

Whichever way he chooses to explain his trust in God's word, the presuppositionalist uses induction in his solution. He's assuming what he sets out to prove. This is a fallacy called begging the question. Any defense of rational induction that depends on a god's promise falls into the same trap.

The insufficiency of the UON

The second problem is that even if we know that nature is uniform, we still haven't done anything to provide rational basis for induction. It seems that the only way we could be certain that an inductive inference would turn out to be true is if the universe was uniform, and we knew everything about it. And this is clearly not the case.

While there are things we don't know about the universe, we can never be sure our inductive inferences will turn out to be true. Perhaps the sun, according to some previously unknown feature of our uniform universe will vanish before the sunrise we predicted has had a chance to happen.

All swans we have seen are white, therefore all swans are white

Induction in a uniform universe can, and does, give false results. Karl Popper's example of the black swan illustrates this. So the uniformity of nature, while being necessary in order for us to gain any advantage from our habit of induction, is useless if you want to establish a rational basis for inductive reasoning.

See all posts relating to presuppositionalism.

Basic

Theists who subscribe to the presuppositionalist school of thought say that atheists can't 'account for' inductive reasoning. They claim that in fact, whenever an atheist uses inductive reasoning, she is borrowing from the Christian world view, because according to them, it's the only world view that can 'account for' the the uniformity of nature, which is needed for inductive reasoning to work.

But, even if the Christian is correct in his claim that an atheist can't 'account for' a given facet of nature that she nevertheless depends upon; this is not the urgent, deal breaking problem that the presuppositionalist tends to paint it as.

Imagine a primitive society where most people believe that spirit ancestors reward the ritual act of watering a plant by causing that plant to grow. A person in this society who didn't believe in the existence of spirit ancestors would still go ahead and water his plants because otherwise they would die.

The skeptic's peers might ask him: 'how can you account for the fact that applying water causes the plant to grow in your world view?'. The skeptic, ignorant of plant biology, would have no answer. His peers might then say 'Every time you water your plants you're borrowing from our world view, because ours is the only system that can account for the connection between applying water to a plant, and that plant's growth'.

I hope the points I wanted to illustrate with this analogy are already clear, but I'll spell them out:

1. Having an explanation does not make your position superior to that of those who may lack one.
2. Not being able to explain a phenomenon doesn't preclude you from legitimately assuming the reliability of that phenomenon
3. Assuming the reliability of a phenomenon without being able to 'account for' it does not mean that you implicitly accept the world view of people claiming that theirs is the only explanation of that phenomenon.
4. The failure of a person to explain a phenomenon doesn't invalidate their world view or render it inconsistent.
5. Acknowledging that you don't have an answer is better than making things up.

Extra credit

Presuppositionalists hold that a theistic world view is the only one that can account for knowledge. In particular, they claim that atheists cannot justify their use of inductive reasoning while God provides a firm epistemological basis, in other words a firm foundation for knowledge.

Uniformity of Nature

The Uniformity of Nature (or the UN as it's often abbreviated) is the name given to the apparent consistency of the universe's physical laws over space and time. Without Uniformity of Nature, the universe would be a chaotic place where the past wouldn't resemble the future.

Inductive reasoning

To use Inductive Reasoning is to make an estimate of how likely a general statement is to be true based on specific knowledge. Inductive reasoning is used when trying to predict future events from knowledge of the past. In a universe without Uniformity of Nature, where the past didn't resemble the future at all, inductive reasoning would be useless.

Presuppositionalists say that god guarantees the Uniformity of nature, and in doing so, provides justification for inductive reasoning.

Van Til, one of the most well known presuppositionalists said:

the existence of the God of Christian theism and the conception of his counsel as controlling all things in the universe is the only presupposition which can account for the uniformity of nature which the scientist needs.

Fallacy 1: The uniformity of nature needs 'accounting for'

When Van Til says that the uniformity of nature needs accounting for he assumes that a chaotic universe is more likely than a uniform one, and that a god is necessary to provide uniformity. But since van til has never seen a universe other than the one we all live in, this is an unfounded assumption. For all we know, it may not be possible for a godless universe to be anything but uniform.

Fallacy 2: The Biblical God is the only presupposition that can 'account for' the uniformity of nature

Far from the Christian god being the only presupposition that can 'account for' the uniformity of nature, it's one of many. There are an infinite number of unlikely sounding assumptions that 'account for' the uniformity of nature such as 'the flying spaghetti monster guarantees the uniformity of nature', or 'the biblical god guarantees the uniformity of nature'. There are also some far more parsimonious presuppositions. Perhaps the simplest one is 'UN is true'.

Fallacy 3: The uniformity of nature is enough to justify inductive reasoning

Presuppositionalists think they have a firm foundation of knowledge that the rest of us lack. But here they are making a double error, because as well as mistakenly believing that the uniformity of nature needs 'accounting for' they seem to believe that the uniformity of nature is sufficient to provide a rational basis for inductive reasoning, when it isn't.

Even in a universe with UN, inductive reasoning can never be epistemologically justified: just because the pen dropped to the floor yesterday doesn't mean that a previously unknown universal law will prevent it from falling to the ground today.

Fallacy 4: Christians can justify the use of induction without begging the question

To demonstrate that the atheist has no basis for assuming the validity of inductive reason, the presuppositionalist asks how we can know that the universe will continue to be uniform. If the answer involves appealing to knowledge of the past then it uses induction to try to validate induction, which is begging the question. The presuppositionalist mistakenly thinks he has a solution to this problem: through revelation, God lets him know that the universe will continue to be uniform.

But how can he be sure that God won't change his mind about UN? The presuppositionalist might cite God's unchanging nature as a guarantee that he won't change his mind.

But what grounds does the Christian have to conclude that god's nature is in fact unchanging?, and that it will continue to be so? Whether he gained knowledge of god's unchanging nature through direct revelation or through scripture, the only way he can say anything about God's nature in the future is to use induction. Appealing to god to solve the problem of induction merely postpones the point at which induction has to be invoked to justify itself–thereby begging the question. Presuppositionalists can't rationally justify their use of induction any more than the rest of us can.

See all posts relating to presuppositionalism.

Incinerating presuppositionalism

An easy argument to refute: Van Tillian, Calvinist, Presuppositionalism