An Enquiry Concerning Human Understanding summary

If everything we know comes from experience, this immediately raises a problem. How could we ever make predictions about the future? After all, we can never experience the future.

Thankfully, we can make use of a handy principle called cause and effect. In the past, we’ve learned that certain events cause other events. All we need to do is transpose that knowledge into the future and we have a method for making predictions about what’s going to happen.

OK, so we might not directly experience a necessary link between cause and effect. But what if we could use reason to find out if there’s a connection?

Well, let’s give it a go. When we’re trying to determine a general theory, like the necessary connection of cause and effect, we usually use inductive reasoning. This is the form of reasoning used when we draw general conclusions from a synthesis of several specific observations. It’s the mode of thinking operating in the background when we make inferences about the future based on past observations, like inferring that fire will burn us again in the future because it has done so in the past.

So Hume has shown that we have no rational basis for making any inferences about the future. But don’t let this put you off planning for tomorrow!

Hume was the first to admit that there’s a natural limit to this kind of skeptical reasoning. We might not be rationally justified in believing the things we do, but that doesn’t stop us from believing them. All of us, and that includes philosophers, use inductive reasoning every day in pretty much every action we take. If we didn’t do this, we simply wouldn’t be able to live.

If it’s true that humans are guided more by instinct than by reason, this raises another problem. If reasoning doesn’t have any influence on our behavior – if we’re just animals governed by blind instinct – then what room does that leave for human freedom?

This is really just a reformulation of the free will vs. determinism debate, which has been raging in philosophy for centuries. The debate considers how it’s possible to reconcile the fact that human actions are causally determined – in this case by our instincts – with our conviction that we have freedom over how we act in any given situation. The concepts of free will and determinism seem completely incompatible with one another.

One of the reasons why Hume’s empirical philosophy was so radical and controversial back in the eighteenth century is that it provided rational grounds for rejecting miracles. Miracles were widely believed at the time and were often taken as evidence for religious doctrines.

Consider this curious example reported by a French cardinal in the seventeenth century. While on one of his travels in the French provinces, the cardinal wrote of having encountered a man who’d apparently regrown his leg. The townsfolk insisted that the man had gone many years with only one leg, but had recovered the missing limb after rubbing holy oil over the stump.

Hume’s empirical philosophy is based on the principle that the only way we can learn about the world is through sensual experience. Of course, Hume admits, this requires that we trust our senses to represent the world as it really is – and it’s far from obvious that they do.

We know, for example, that our senses often deceive us, such as when a boat’s oar appears crooked in the water, or when an object appears doubled when it’s held too close to the eyes.