Causality & Determinism

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Causality and Determinism: Tension, or Outright Conflict?
Carl Hoefer
ICREA and Universidad Autònoma de Barcelona
Draft October 2004

Abstract: In the philosophical tradition, the notions of determinism and causality are strongly
linked: it is assumed that in a world of deterministic laws, causality may be said to reign
supreme; and in any world where the causality is strong enough,determinism must hold. I will
show that these alleged linkages are based on mistakes, and in fact get things almost completely
wrong. In a deterministic world that is anything like ours, there is no room for genuine
causation. Though there may be stable enough macro-level regularities to serve the purposes of
human agents, the sense of “causality” that can be maintained is one that will at bestsatisfy
Humeans and pragmatists, not causal fundamentalists.

Introduction. There has been a strong tendency in the philosophical literature to conflate
determinism and causality, or at the very least, to see the former as a particularly strong form of
the latter. The tendency persists even today. When the editors of the Stanford Encyclopedia of
Philosophy asked me to write the entry ondeterminism, I found that the title was to be “Causal
determinism”.1
I therefore felt obliged to point out in the opening paragraph that determinism actually
has little or nothing to do with causation; for the philosophical tradition has it all wrong. What I
hope to show in this paper is that, in fact, in a complex world such as the one we inhabit,
determinism and genuine causality are probablyincompatible with each other. After we see why
this is so, we can appreciate better the different metaphysical options available to philosophers
hoping to understand the complex issues concerning laws of nature, causality, and physical
theory.
At first blush it should seem strange to be told that determinism and genuine causality
are incompatible.2 After all, let’s consider a simple possibleworld governed by Newtonian
mechanics, consisting of nothing but a box with rigid walls, and a few billiard balls inside
colliding elastically with the walls and with each other. This possible world is surely

1

Hoefer (2003), http://plato.stanford.edu/entries/determinism-causal/

2

I will explain below what is meant by the modifier “genuine” here.

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deterministic (none of thepathological elements of Newtonian physics are permitted, here)3, and
what could be a more standard example of cause-effect relations than that old cliché, billiardball collisions? Accepting these claims for a moment, what this shows is just that in very
simple, idealized worlds, determinism may be able to coexist with genuine causality. My target
is to consider a very different kind of possibleworld: namely, a world as rich and complex and
apparently-irregular as ours is. We will see what problems are brought by this richness and
complexity, below.
But surely there is more to say in favor of the compatibility of determinism and causality
than just our toy billiard-ball-world example? In fact, isn’t one precise way of presenting
determinism this: If the world is governed bydeterministic laws, then an[y complete] earlier
state of the whole world may be considered a sufficient cause of a[ny] later state of the world, in
all details. If this isn’t genuine causality, then what is?
But this isn’t genuine causality, in anything remotely like the senses of “X caused Y” or
“P’s cause Q’s” that we employ in everyday life or in science. First, consider that in all
reasonableexamples of deterministic theories we have in hand, the determinism is bidirectional: future states of the world entail past events completely, as well as vice-versa. Yet it
strains the notion of “cause” past the breaking point, to say that we should consider the state of
the world 1 billion years from now as the cause of all our current events and actions. (Here, by
the way, we see one reason why...