It sounds so true. People seem to take such comfort from that phrase's wisdom. There's something proudly accepting and resolved in their tone when they declare it, as though they're sharing a hard-earned profound lesson.
What it means though is very much up in the air. And therein lies a tale of our era's confusion regarding causality, or what we mean by "a reason."
Here then is brief history of the confusion.
Aristotle, using house-building as an example developed what he thought was a comprehensive list of the kinds of reasons why anything happens:
Material cause (what a house is made of)
Formal cause (the blueprint or plan for putting the materials together)
Efficient cause (the nail-banging done by the carpenter; the "this-hits-that" kind of cause we think of as cause and effect)
Final cause (the purpose or goal for building the house)
For over a thousand years following Aristotle, people focused primarily on final and efficient cause, thinking everything had its purpose, but also accumulating practical intelligence about the "this-hits-that" of efficient cause. In a way, nothing has changed. We still rely mostly on these two kinds of causal explanations. Both are implied by "everything happens for a reason." Do things happen today so as to achieve some later purpose? That's what final cause suggests. Or do things happen today because they are the consequent effect of earlier causes. If so, "a reason" is an appeal to efficient cause.
Think about the two ways you can answer a "Why?" question. Why are the birds flying South? To stay warm in the coming winter is a final cause answer. Because their instincts generated biochemical reactions that switch on migration behavior is an efficient cause answer.
In the West throughout the early middle ages final causes as understood by the Catholic Church were what really mattered. God had purposes and put them into every living and non-living thing. You could explain how anything behaved simply by saying that it was behaving as God intended it to behave.
In the Islamic East, God's purposes--his final causes--were also very important, but Muslims saw no incompatibility in actively investigating efficient cause too. The Muslims were scientists long before science took off in the West.
Then the eleventh century Al Ghazali, an important Islamic philosopher pointed out that actually, final and efficient cause were fundamentally incompatible. Either God's purposes (final causes) are inviolable, or nature's laws (efficient cause) are inviolable. If there's any difference between God's final purposes and nature's efficient laws--for example if God can intervene and miraculously break nature's laws--then they can't both be inviolable.One must ultimately trump the other.
In response, the Islamic East decided God and his purposes trumped efficient cause. Islam backed off of science. In the West, within a few hundred years we took the opposite path, deciding that final cause was not even a rational concept (How can the future cause the present? That would be some inexplicable "backward causality.") Efficient cause became the one true kind of cause. That's why Western science attempts to explain everything in terms of the "this-hits-that," of efficient causes. To most scientists today, there's no final cause or purposes at all. Everything can and must be explained exclusively in terms of efficient cause's billiard ball like "this-hits-that" behavior.
So what do we mean when we say "everything happens for a reason"? Do we mean we mean efficient or final cause?
If we mean there's an efficient cause reason for everything, then all the saying means is that every behavior is a consequence of actions that preceded it. It's like saying "cause and effect rules."
That doesn't seem very profound.
If we mean everything happens for a final cause reason, then every behavior serves some objective, goal or purpose. That's more profound perhaps but it opens a worm-can of wonder. Good purposes? Bad purposes? Whose purposes? And what are you supposed to do about it since your behavior too, whatever it may be, happens for a reason.
Say "everything happens for a reason," and people nod knowingly even though some take it to mean everything happens because it was efficiently caused, and others take it to mean everything serves a purpose. Maybe we prefer to keep the concept ambiguous. It makes for polite agreement even if it hides a major disagreement.
Whether reason is taken to mean final or efficient cause, the psychological effect of saying "Everything happens for a reason" is the same. At the emotional level it means surrender, relax, it's beyond your control. Accept things as they are because they happen for a reason.
It's natural that we would collect and share sayings that mean surrender. There are others: "It's God's will," for example--that's definitely an appeal to a final cause. Or how about "Shit happens"? That's definitely an appeal to efficient cause. Some ways to say "surrender" are appeals to final causes or higher purposes; some to efficient causes or natural laws, and some are ambiguous. "It's Karma" can mean that a particular behavior is rewarded or punished depending on its contribution higher purpose and final cause. Or it can simply mean that a particular behavior is the cause and effect consequence of what preceded it.
People may be confused about what's meant by "everything happens for a reason," but so are scientists. Scientist are committed to the West's elimination of final cause in explanations. But of course they're also people. So even though they want to explain everything in terms of efficient cause, they slip and talk about why things are useful, for example how a body part functions serve an organism's purposes.
Researchers working on the emergence of purpose don't see this slipping into final-cause talk as slipping at all, but rather as evidence that we've got more thinking to do about reasons. Ever since Al Ghazali noticed that you can't have it both ways, we've tried to clarify what is meant by "cause" or "reason" by eliminating one kind of cause or the other. The Islamic East chose God's final cause; the scientific West chose nature's efficient cause. And for a while that was fine. Even more than fine in the West because ignoring final cause allowed us to figure out a lot about efficient cause. We've made so much progress in figuring out nature's "this-hits-that" laws of efficient cause that most scientists think it's only a matter of time before we explain everything in efficient causal terms. But emergence scientists say no, we're coming up to a hard limit. We're beginning to fake it, pretending, for example that your behavior is just efficient cause when really, for humans and indeed all living things, final cause is real. Your purposes change your behavior. Your behavior can't be explained by efficient cause alone.
Not all behavior requires a final cause explanation, but some does, and that, according to emergentists, must be explained. Despite Al Ghazali's either/or framing, we're going to have to be able to have it both ways. The universe at its origins really does seem to operating on efficient cause alone. But living things nonetheless present behavior that can't be explained without reference to purposes. In other words, purpose (final cause) is real even if it doesn't serve a grand purpose.
If you like to have interesting conversations and debates, next time you hear someone say "Everything happens for a purpose," ask them what they mean. By "reason" do they mean because something caused it (efficient cause) or do they mean that it is serving some future goal (final cause)? And if they mean everything serves some higher purpose, is it necessarily a good one? Or do they mean that things happen for good and bad reasons?
The reason I bring this all up is that it serves a higher purpose of mine. In a coming article I'll explain how emergentists, rethinking another of Aristotle's causes, formal cause, begin to explain how you get final cause out of efficient cause. In other words how final cause could emerge from efficient cause.