Constant conjunction of events and probability

Question

Hume argued that it's impossible to say that event A causes event B. For all we know, everytime event B is directly followed by event A, we could be witnessing the "constant conjunction of events." Therefore, although we regularly rely on what we perceive to be causation in order to predict outcomes, those predictions do not stand on the same ground as things that are necessarily true by definition (e.g., 1+1=2).

However, would Hume concede that certain events have a higher probability of occurring based on past events? Is it much more likely that a rock will break a window when thrown with a certain force than not? Or is that a fallacious argument grounded in confusing the "constant conjunction of events" (of always seeing rocks break windows) with causality?

Answer 1

William Edward Morris and Charlotte R. Brown present a view of Hume's idea of causation that may help resolve the OP's question whether probability could justify causal inference through reason or understanding.

As the OP notes, effects are not necessarily true given past events believed to be causes of those effects. So, one cannot justify causal inference through relations of ideas, that is, there is no necessary connection between past events and future events.

To consider probability is to consider matters of fact rather than relations of ideas as a rational justification for causality. According to Morris and Brown, Hume also rejects matters of fact, that is, probability, as a rational justification for causal inference: (Section 5.1)

Hume argues that there is no probable reasoning that can provide a just inference from past to future. Any attempt to infer [a future prediction] from [a past experience] by a probable inference will be viciously circular—it will involve supposing what we are trying to prove.

Hume spells out the circularity this way. Any reasoning that takes us from [a past experience] to [a future prediction] must employ some connecting principle that connects the past with the future. Since one thing that keeps us from moving directly from past to future is the possibility that the course of nature might change, it seems plausible to think that the connecting principle we need will assure us that nature is uniform—that the course of nature won't change—something like the uniformity principle:

Establishing this uniformity principle is what prevents both relations of ideas (necessary truths) and matters of fact (probability) from providing a justification of causal inference using reason or understanding.

Hume offers "custom or habit" as alternatives to reason and understanding to explain why we make causal inferences: (Section 5.2):

Since we're determined—caused —to make causal inferences, then if they aren't “determin'd by reason”, there must be “some principle of equal weight and authority” that leads us to make them. Hume maintains that this principle is custom or habit:

They quote Hume:

whenever the repetition of any particular act or operation produces a propensity to renew the same act or operation … we always say, that this propensity is the effect of Custom. (EHU 5.1.5/43)

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Here are the questions:

However, would Hume concede that certain events have a higher probability of occurring based on past events? Is it much more likely that a rock will break a window when thrown with a certain force than not? Or is that a fallacious argument grounded in confusing the "constant conjunction of events" (of always seeing rocks break windows) with causality?

Hume accepts "custom or habit". He does not accept probability through reason or understanding. That is, neither relations of ideas nor matters of fact (probability) provide a rational justification for causal inferences.

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Morris, William Edward and Brown, Charlotte R., "David Hume", The Stanford Encyclopedia of Philosophy (Spring 2017 Edition), Edward N. Zalta (ed.), URL = https://plato.stanford.edu/archives/spr2017/entries/hume/.

Answer 2

According tor David Hume :

our awareness of causation (or power, force, efficacy, necessity, and so forth - he holds all such terms to be equivalent) is a product of experience [...]

what this awareness consists in ? What is meant when some event is judged as cause and effect? Strictly speaking, for Hume, our only external impression of causation is a mere constant conjunction of phenomena, that B always follows A, and Hume sometimes seems to imply that this is all that causation amounts to. (And this notion of causation as constant conjunction is required for Hume to generate the Problem of induction .) Nevertheless, ‘causation’ carries a stronger connotation than this, for constant conjunction can be accidental and therefore doesn’t get us the necessary connection that gives the relation of cause and effect its predictive ability. We may therefore now say that, on Hume’s account, to invoke causality is to invoke a constant conjunction of relata whose conjunction carries with it a necessary connection.

For Hume human reasoning involves only relations of ideas and matters of fact. Matters of fact can be either particular specific observation or

Claims about states of affairs not directly observed.

[These ones] would include both predictions and the laws of nature upon which predictions rest. We cannot claim direct experience of predictions or of general laws, but knowledge of them must still be classified as matters of fact [i.e. empirical].

All predictions must involve causality and must therefore be of [the above] category. But what justifies them?

This is the gist of so-called Humean Problem of induction.

The probabilistic approach is for sure one of the candidate answer to the problem.