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More Heat Than Light: Economics as Social
Physics, Physics as Nature's Economics. By
Philip Mirowski. Cambridge: Cambridge
University Press, 1989.

of physics, but Mirowski’s brilliant work is no ordinary book.
He contends that economics, culminating in the currently
dominant neoclassical school, has throughout its history been con-
trolled by a metaphor. Most economists regard their discipline as a
science; since, in the common understanding, physics is the best
developed of the sciences, economics ought to be modeled on physics.
Mirowski’s radical thesis is that the model of physics has determined
in detail the sum and substance of economic theory from the Physio-
crats down to the present.

Mirowski has an even more ambitious goal than the presentation
of his revolutionary view of economics. He writes not as a detached
observer but as a vigorous partisan. He strongly opposes the control
of economics by physics. Economists, in pursuit of their futile ideal
of rigor, have misunderstood physics and generated “science, falsely
so-called.” Mirowski himself has enlisted in the institutionalist camp,
but his own views of correct theory do not receive much discussion in
More Heat Than Light.! He comes not to praise neoclassicism, but to
bury it.

Mirowski contends that conservation principles are the leitmotif
in the growth of modern physics. Very roughly, a conservation prin-
ciple requires that some quantity, e.g., mass or energy, be kept
constant in a given system. To take a case often used by nineteenth-
century physicists, a perpetual motion machine disobeys the law of

} er books on the history of economics begin with a discussion

His institutionalism is discussed in more detail in his Against Mechanism: Protect-
ing Economics from Science (Tottowa: Rowman & Littlefield, 1988), esp. pp. 57-93,
106-33, and 191-232.

The Review of Austrian Economics, Vol. 5, No. 1 (1991): 123-128
ISSN 0889-3047

123


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124 The Review of Austrian Economics, Vol. 5, No. 1

energy conservation since it requires new energy to be generated out
of nothing.

Mirowski once more writes not as a mere observer of the scene.
He thinks that physics has placed undue reliance on conservation
laws. They cannot be exactly stated; and the proofs of the laws, e.g.,
the impossibility of perpetual motion, rest more on assertion than
argument. Even more importantly, a look at the history of physics
shows that conservation principles have died “the death of a thousand
qualifications.”

The sad tale begins with Descartes, who according to Mirowski
made the conservation of mass basic to his program of reducing the
physical world to matter in motion. I am inclined to think that
Mirowski overemphasizes Descartes’ philosophical adherence to con-
servation of mass. He did not believe that minds were physical. One
of the minds, namely God, creates the physical world and constantly
upholds it. Further, even within physics itself, Descartes’s “exten-
sion” bears closer resemblance than Mirowski allows to the field
concept that in his view emerged only in the nineteenth century.’

Oddly, Newton plays no role in our author’s version of the story
of physics, on the ground that he did not explicitly use conservation
principles (p. 404). But readers inclined to complain that physics
without Newton is like Hamlet without the Danish prince, will be
surprised at the coherence and complexity of Mirowski’s account. The
importance of conservation laws lies principally in the fact that they
allow the use of certain mathematical techniques, such as variational
principles.

The fly-in-the-ointment is that the conservation laws had to be
constantly modified and restricted, since otherwise they fail to work.
Instead of operating with physical substance, physics in the nine-
teenth century turned to the impalpable notion of the field. The use
of the field concept made possible the employment of powerful math-
ematical tools, such as Hamiltonians and Lagrange equations, at the
cost of considerable difficulty in the statement of exactly what was
supposed to be conserved.

Other developments, such as the rise of entropy, required further
restrictions on conservation. Physicists at the beginning of the twen-
tieth century could no longer readily console themselves over the
surrender of conservation with their ever-refined formalism. Henri
Poincaré showed that only under certain very limited conditions can

2This is a phrase used by the philosopher Antony Flew.

3A minority view, favored by Hiram Caton, does take Descartes to be a materialist,
but Mirowski does not refer to this interpretation.


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Book Reviews 125

the mathematical methods cited above be used. As the reader will by
now expect, the rise of special and general relativity and quantum
mechanics in the present century has further complicated the story
and altered the meaning of conservation laws. Mirowski goes so far
as to suggest that physicists have really abandoned conservation but
cling to an outworn metaphor.

All very interesting, no doubt; but what has this to do with
economics? Mirowski’s answer is practically everything. Economists
have directly translated the models of physics in use in their time
into economic categories. (Incidentally, this does not exclude the
influence of economic concepts in physics.) Why, e.g., did Adam Smith
define wealth as stock (p. 166)? Not because this definition was
dictated to him by his observation of the economy. Quite the contrary,
he was influenced by Cartesian physics, and stock, in Smith’s view
the substance of value, corresponds to the mass that is conserved in
Cartesian physics.

Is Mirowski correct? I find it hard to decide. Smith does not say
that he was transferring a physical concept to economic theory; and,
even if he did, it does not follow that Smith’s description of the
economy is inaccurate. Mirowski emphatically dissents; in his view,
the actual economical world plays only a limited role in economic
theorizing. On Mirowski’s behalf, however much one may think him
mistaken about a particular economist, his piling up of case after case
of parallelism between physics and economics will impress even the
most skeptical reader.

Smith, as briefly suggested, believed that economic value was a
substance. This notion dominated classical economics. Although
Mirowski thinks extremely highly of Marx, calling him “an epoch-
making economist” (p. 179), he shows very effectively that resort to
value as substance proved Marx’s undoing.

Once more the question arises: did Marx use this notion of value
because he was consciously seeking a model of the economy based on
the physical sciences? The case seems to me suggestive but unproven.
Mirowski stands on much firmer ground, however, in his treatment
of the neoclassicals.

When the field concept came to dominate physics, many scientists
in a flush of enthusiasm thought that a new discipline, energetics,
would prove capable of unifying both the physical and the social
sciences. As the name suggests, energy was the key to the mystery;
and here the application to economics is clear and straightforward.
Utility, the basic concept of neoclassical theory, is identical with
energy.

Mirowski’s claim is startling, but he documents to the hilt that


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126 The Review of Austrian Economics, Vol. 5, No. 1

Léon Walras and William Stanley Jevons, both of whom had scientific
backgrounds, directly intended to use the physics of their day to
transform economics into an exact science. Even more clearly, Irving
Fisher, whose 1892 doctoral dissertation at Yale remains, if the
reader will forgive me, a classic of neoclassicism, made crystal clear
his goal. Fisher himself drew detailed parallels between mechanics
and economics. His thesis was written, not under the supervision of
an economist, but with J. Willard Gibbs, one of the greatest of all
American physicists, as its director.

In the neoclassical view, utility is a vector-field corresponding to
energy. Mirowski ably shows how the entire neoclassical edifice falls
into place once one grasps this basic idea. But this does not vindicate
neoclassicism: far from it. Utility has to be regarded as an entity
separate from the goods and services people consume, in a way that
defies common sense. Such eminent neoclassicals as Milton Fried-
man were at one time skeptical about the validity of this notion of
utility (p. 366).

An obvious neoclassical rejoinder is that whatever the intuitive
implausibility of utility as a field concept, the system works.
Mirowski dissents and challenges the school at its point of greatest
pride, its use of advanced mathematics. He finds in the neoclassical
system a profusion of incorrect assumptions and arbitrary errors.
I cannot present at length the technical details of Mirowski’s case
but can indicate only a few of its highlights. The system is unable
to explain production: it is goods and services that are produced,
not energy or utility. Neoclassicals have been unable effectively to
account for production through their field concept. Further, the
system wrongly assumes that utility must have certain features
needed to make mathematical manipulation easier. Unless these
features are present, the powerful Hamiltonian techniques men-
tioned earlier cannot be used. But the assumption that utility has
these features is without basis. Further, the system depends on the
law of one price, another assumption Mirowski considers arbitrary.
Hermann Laurent, a noted mathematician, pointed out some of
these errors to Walras; but Walras could not grasp the points at
issue.

Mirowski’s criticisms appear penetrating and will give neoclassi-
cals a difficult time. I am not entirely convinced, however, by his
objections to the law of one price. This law states that a single price
for each commodity tends to prevail on the market. Mirowski seems
right that the law is, from the point of view of mathematics, arbitrary.
But he too readily dismisses the “common-sense” point that competi-
tion among traders will eliminate differences in prices. For once one


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Book Reviews 127

can retort to Mirowski that his vague references to strategic consid-
erations and game theory (p. 236) are no substitute for a rigorous
refutation of the law.

Of course, common-sense arguments have no place in a system
that purports to be completely mathematical, and to the extent that
neoclassicism has this goal, Mirowski’s challenge to the law of single
price is perfectly justified. But does contemporary economics alto-
gether eschew arguments not based on physics? It will hardly do to
dismiss the use of such arguments just because they do not conform
to Mirowski’s own picture of neoclassicism.

Regardless of this and other details, Mirowski’s case is formi-
dable. How can economics escape its longstanding bewitchment by
physics? Readers familiar with Austrian economics cannot fail to
note that the Austrian school avoids all of the errors that Mirowski
finds in both classical substance accounts of value and neoclassical
energetic theories of utility. Mirowski rightly notes that Carl Men-
ger “cannot be considered a neoclassical economist” (p. 261), since
he repudiated the imitation of physical science. But evidently
viewing Menger’s path as leading nowhere, he does not give a
detailed analysis of the Austrian system. (Elsewhere, he refers
briefly to Hayek but never to Mises.) Had Mirowski done so, he
would have found the answer to his difficulties. In the Austrian
view, exchange takes place only where each party values the good
he gains more than the good he surrenders. By repudiating the
spurious principle that exchange is an equality, the problem of
conservation of utility disappears. Further, the best developed
version of Austrianism, that of Mises and Murray Rothbard, views
utility as simply a ranking of goods. It is not a mysterious sub-
stance or field; and there is no problem of integrating production
and distribution. The theory always operates with preferences for
concrete goods and services, not the quintessence “utility” to which
Mirowski objects. With this school, I suggest, not with the institu-
tionalism Mirowski favors, lies the future of economics.

There is much else in this outstanding work that merits discus-
sion. Influenced by the anthropologist Mary Douglas, Mirowski be-
lieves that both economics and physics take many of their concepts
from the human body; and he presents an elaborate scheme of the
evolution of these concepts. Further, he views theories as metaphors
that are imposed on reality. Like Donald McCloskey and Richard
Rorty, he rejects a realistic theory of knowledge. I do not think this
is the place to discuss these views at length, and any attempt to do
so is handicapped by the failure of our author to define “metaphor.”
One question that does come to mind, however, is this: is not


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128 The Review of Austrian Economics, Vol. 5, No. 1

Mirowski’s continual claim that precisely the same conservation laws
are present in both physics and economics itself an instance of just
the sort of domination by the metaphor of conservation he complains
of in others? For Mirowski, it is apparently the conservation laws
that must be conserved.

The book is immensely stimulating and suggestive. It is must
reading for all economists and intellectual historians.

David Gordon
The Ludwig von Mises Institute