Causal determinism is, roughly speaking, the idea that every event is necessitated by antecedent events and conditions together with the laws of nature. The idea is ancient, but first became subject to clarification and mathematical analysis in the eighteenth century. Determinism is deeply connected with our understanding of the physical sciences and their explanatory ambitions, on the one hand, and with our views about human free action on the other. In both of these general areas there is no agreement over whether determinism is true (or even whether it can be known true or false), and what the import for human agency would be in either case.3. The Epistemology of Determinism
3.1 Laws again
3.2 Experience
3.3 Determinism and Chaos
3.4 Metaphysical arguments
4. The Status of Determinism in Physical Theories
4.1 Classical mechanics
4.2 Special Relativistic physics
4.3 General Relativity (GTR)
4.4 Quantum mechanics
5. Chance and Determinism
6. Determinism and Human Action
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[size=30]1. Introduction
In most of what follows, I will speak simply of
determinism, rather than of
causal determinism. This follows recent philosophical practice of sharply distinguishing views and theories of what causation is from any conclusions about the success or failure of determinism (cf. Earman, 1986; an exception is Mellor 1994). For the most part this disengagement of the two concepts is appropriate. But as we will see later, the notion of cause/effect is not so easily disengaged from much of what matters to us about determinism.
Traditionally determinism has been given various, usually imprecise definitions. This is only problematic if one is investigating determinism in a specific, well-defined theoretical context; but it is important to avoid certain major errors of definition. In order to get started we can begin with a loose and (nearly) all-encompassing definition as follows:
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- اقتباس :
- Determinism: The world is governed by (or is under the sway of) determinism if and only if, given a specified way things are at a time t, the way things go thereafter is fixed as a matter of natural law.
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The italicized phrases are elements that require further explanation and investigation, in order for us to gain a clear understanding of the concept of determinism.
The roots of the notion of determinism surely lie in a very common philosophical idea: the idea that
everything can, in principle, be explained, or that
everything that is, has a sufficient reason for being and being as it is, and not otherwise. In other words, the roots of determinism lie in what Leibniz named the Principle of Sufficient Reason. But since precise physical theories began to be formulated with apparently deterministic character, the notion has become separable from these roots. Philosophers of science are frequently interested in the determinism or indeterminism of various theories, without necessarily starting from a view about Leibniz' Principle.
Since the first clear articulations of the concept, there has been a tendency among philosophers to believe in the truth of some sort of determinist doctrine. There has also been a tendency, however, to confuse determinism proper with two related notions:
predictability and
fate.Fatalism is the thesis that all events (or in some versions, at least some events) are destined to occur no matter what we do. The source of the guarantee that those events will happen is located in the will of the gods, or their divine foreknowledge, or some intrinsic teleological aspect of the universe, rather than in the unfolding of events under the sway of natural laws or cause-effect relations. Fatalism is therefore clearly separable from determinism, at least to the extent that one can disentangle mystical forces and gods' wills and foreknowledge (about
specific matters) from the notion of natural/causal law. Not every metaphysical picture makes this disentanglement possible, of course. But as a general matter, we can imagine that certain things are fated to happen, without this being the result of deterministic natural laws alone; and we can imagine the world being governed by deterministic laws, without anything at all being
fated to occur (perhaps because there are no gods, nor mystical/teleological forces deserving the titles
fate or
destiny, and in particular no intentional determination of the “initial conditions” of the world). In a looser sense, however, it is true that under the assumption of determinism, one might say that
given the way things have gone in the past, all future events that will in fact happen are already
destined to occur.
Prediction and determinism are also easy to disentangle, barring certain strong theological commitments. As the following famous expression of determinism by Laplace shows, however, the two are also easy to commingle:
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- اقتباس :
- We ought to regard the present state of the universe as the effect of its antecedent state and as the cause of the state that is to follow. An intelligence knowing all the forces acting in nature at a given instant, as well as the momentary positions of all things in the universe, would be able to comprehend in one single formula the motions of the largest bodies as well as the lightest atoms in the world, provided that its intellect were sufficiently powerful to subject all data to analysis; to it nothing would be uncertain, the future as well as the past would be present to its eyes. The perfection that the human mind has been able to give to astronomy affords but a feeble outline of such an intelligence. (Laplace 1820)
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In this century,
Karl Popper (1982) defined determinism in terms of predictability also, in his book
The Open Universe.
Laplace probably had God in mind as the powerful intelligence to whose gaze the whole future is open. If not, he should have: 19
th and 20
th century mathematical studies showed convincingly that neither a finite, nor an infinite but embedded-in-the-world intelligence can have the computing power necessary to predict the actual future, in any world remotely like ours. But even if our aim is only to predict a well-defined subsystem of the world, for a limited period of time, this may be impossible for any reasonable finite agent embedded in the world, as many studies of chaos (sensitive dependence on initial conditions) show. Conversely, certain parts of the world could be
highly predictable, in some senses, without the world being deterministic. When it comes to predictability of future events by humans or other finite agents in the world, then, predictability and determinism are simply not logically connected at all.
The equation of “determinism”with “predictability” is therefore a
façon de parler that at best makes vivid what is at stake in determinism: our fears about our own status as free agents in the world. In Laplace's story, a sufficiently bright demon who knew how things stood in the world 100 years before my birth could predict every action, every emotion, every belief in the course of my life. Were she then to watch me live through it, she might smile condescendingly, as one who watches a marionette dance to the tugs of strings that it knows nothing about. We can't stand the thought that we are (in some sense) marionettes. Nor does it matter whether any demon (or even God) can, or cares to, actually predict what we will do: the existence of the strings of
physical necessity, linked to far-past states of the world and determining our current every move, is what alarms us. Whether such alarm is actually warranted is a question well outside the scope of this article (see Hoefer (2002a), Ismael (2016) and the entries on
free will and
incompatibilist theories of freedom). But a clear understanding of what determinism is, and how we might be able to decide its truth or falsity, is surely a useful starting point for any attempt to grapple with this issue. We return to the issue of freedom in section 6,
Determinism and Human Action, below.
[size=30]2. Conceptual Issues in Determinism[/size]
Recall that we loosely defined causal determinism as follows, with terms in need of clarification italicized:
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- اقتباس :
- Determinism: The world is governed by (or is under the sway of) determinism if and only if, given a specified way things are at a time t, the way things go thereafter is fixed as a matter of natural law.
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2.1 The World
Why should we start so globally, speaking of the
world, with all its myriad events, as deterministic? One might have thought that a focus on individual events is more appropriate: an event
E is causally determined if and only if there exists a set of prior events {
A,
B,
C …} that constitute a (jointly) sufficient cause of
E. Then if all—or even just
most—events
E that are our human actions are causally determined, the problem that matters to us, namely the challenge to free will, is in force. Nothing so global as states of the whole world need be invoked, nor even a
complete determinism that claims
all events to be causally determined.
For a variety of reasons this approach is fraught with problems, and the reasons explain why philosophers of science mostly prefer to drop the word “causal” from their discussions of determinism. Generally, as John Earman quipped (1986), to go this route is to “… seek to explain a vague concept—determinism—in terms of a truly obscure one—causation.” More specifically, neither philosophers' nor laymen's conceptions of
events have any correlate in any modern physical theory.
[1] The same goes for the notions of
cause and
sufficient cause. A further problem is posed by the fact that, as is now widely recognized, a set of events {
A,
B,
C …} can only be genuinely
sufficient to produce an effect-event if the set includes an open-ended
ceteris paribus clause excluding the presence of potential disruptors that could intervene to prevent
E. For example, the start of a football game on TV on a normal Saturday afternoon may be sufficient
ceteris paribus to launch Ted toward the fridge to grab a beer; but not if a million-ton asteroid is approaching his house at .75
c from a few thousand miles away, nor if his phone is about to ring with news of a tragic nature, …, and so on.
Bertrand Russell famously argued against the notion of cause along these lines (and others) in 1912, and the situation has not changed. By trying to define causal determination in terms of a set of prior sufficient conditions, we inevitably fall into the mess of an open-ended list of negative conditions required to achieve the desired sufficiency.
Moreover, thinking about how such determination relates to free action, a further problem arises. If the
ceteris paribus clause is open-ended, who is to say that it should not include the negation of a potential disruptor corresponding to my freely deciding not to go get the beer? If it does, then we are left saying “When
A,
B,
C, … Ted will then go to the fridge for a beer, unless
D or
Eor
F or … or Ted decides not to do so.” The marionette strings of a “sufficient cause” begin to look rather tenuous.
They are also too short. For the typical set of prior events that can (intuitively, plausibly) be thought to be a sufficient cause of a human action may be so close in time and space to the agent, as to not look like a threat to freedom so much as like enabling conditions. If Ted is propelled to the fridge by {seeing the game's on; desiring to repeat the satisfactory experience of other Saturdays; feeling a bit thirsty; etc}, such things look more like
good reasons to have decided to get a beer, not like external physical events far beyond Ted's control. Compare this with the claim that {state of the world in 1900; laws of nature} entail Ted's going to get the beer: the difference is dramatic. So we have a number of good reasons for sticking to the formulations of determinism that arise most naturally out of physics. And this means that we are not looking at how a specific event of ordinary talk is determined by previous events; we are looking at how
everything that happens is determined by what has gone before. The state of the world in 1900 only entails that Ted grabs a beer from the fridge by way of entailing the entire physical state of affairs at the later time.[/size]
Causal Determinism
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