3 min and 55 sec to read, 980 words

What is it we predict when we predict something? The perhaps most common belief seems to be that we predict events, so that we predict event E will occur with some probability P. But how do we divide the world into events? What is an event? It cannot be a single moment in time, isolated from all other moments, since that would mean that we could not predict it in any meaningful way. A prediction relies on a web of causality of some sort, or at least a web of some kind of connections to the event that we are trying to predict — an event is not an isolated moment, it is the product of at least a set of other moments. ¹ There is surely some kind of connection with Quine’s web of belief here. See on his holism: https://plato.stanford.edu/entries/quine/ and equally there is a connection to Whitehead’s philosophy of process and event here, see https://philarchive.org/archive/MASRTC-3

But this presents another problem: how do we decide which events E(1)…E(N) go into the set of relevant preceding events when we want to predict a specific event E (x)? One image here would be that of a landscape – where we are predicting a point in the landscape on the basis of other adjacent points, and even if the entire landscape can contribute to the prediction’s accuracy, it does so only marginally. Predicting our event requires understanding the adjacent event space in some way – and determining that space is really hard (this is sort of what super forecasters do when they turn a prediction into a Fermi-problem with a set of factors that will impact the probability of an event. Identifying the baseline is a bit like identifying the neighbourhood of the event, perhaps).

In some sense, however, all predictions are predictions of worlds. If I predict Bill Clinton will win the election I predict that we will be in a world W such that Bill Clinton is president of the United States in that world. “World” here is shorthand for the entire state space we are in, among all possible state spaces of the universe (indeed, we should probably also be able to say that we are predicting universes).

So which is it? Are we predicting events or worlds? Is there a difference? Does it matter? It seems as if the mental image we have when we are predicting is different – predicting an event is like predicting which card will be drawn from a deck, whereas predicting a world seems more like envisioning a future wholesale. But that is not enough to argue that there is a meaningful difference, I think. But there is something about this distinction that still makes sense, if nothing else as a tool for checking our predictions. If we predict an event, it should be compatible with the world we predict overall — and so the prediction of a point in the landscape needs to be compatible with what we know about the space of possible landscapes. If I predict an event E that is not possible in any conceivable world, my prediction is a curious kind of mistake.

Equally, we may benefit from remembering that adjacency is not determined only by proximity in space and time — some events can be predicted by looking at something that happened a long time ago, far away. Some people’s actions are determined by events and experiences in their childhood, for example, and predicting what they will do next may depend not on what they have just done, but by who they are (identity-based predictions are in a sense world-predictions. A person who loves dogs, cats and other animals may have had a bad encounter with a snake in their childhood and may react badly to a snake even though they could have been thought to love animals based on their recent interactions).

There is a lot of connections with Nelson Goodman’s philosophy here, I think. His notion of “world versions” seem especially relevant to the philosophy of predictions. In some way we make worlds when we predict, and those worlds are narratively described, and we then predict the narrative rather than the event. And this seems important as we keep exploring this subject: events are atomistic, propositional, and our thinking is not propositional. When we predict something we rarely predict a proposition — even though this is often how prediction is framed.

A simple example would be the prediction that Bill Clinton would be president. That prediction might be formulated as “the probability P that the proposition “Bill Clinton is president” is true at time t” — but when we predict we predict stories, or narratives, so it is more like “the probability P that the story that ends with Bill Clinton winning the election at time T ends up being true”. This matters, since the unit of prediction matters for understanding how good predictions are composed. ² This leads us to the questions about rationality. Kahneman’s and Tversky’s bankperson Linda is an interesting example that I wrote more about here. See e.g. here.

Exploring a philosophy of predictions requires understanding what it is that is predicted – events or worlds, propositions or stories (narratives).³ Or if we should speak about predicting “a web” or “a tree” in some way. See interesting discussion here: https://link.springer.com/chapter/10.1057/9781137472519_8

These are questions of how we configure a problem. Problem configuration is an undervalued question that would be worth more attention — and it is not just about framing, either — even if the two are closely related.⁴ Note to self: it would be good to explore the configuration of problems more in detail – and how it relates to epistemology.

Footnotes and references

• 1
  There is surely some kind of connection with Quine’s web of belief here. See on his holism: https://plato.stanford.edu/entries/quine/ and equally there is a connection to Whitehead’s philosophy of process and event here, see https://philarchive.org/archive/MASRTC-3
• 2
  This leads us to the questions about rationality. Kahneman’s and Tversky’s bankperson Linda is an interesting example that I wrote more about here. See e.g. here.
• 3
  Or if we should speak about predicting “a web” or “a tree” in some way. See interesting discussion here: https://link.springer.com/chapter/10.1057/9781137472519_8
• 4
  Note to self: it would be good to explore the configuration of problems more in detail – and how it relates to epistemology.