Know to foresee, foresee to act

Auguste Comte 1798 · 1857Know only facts: the positive age of science.

What it claims

Acting effectively requires foreseeing from observed laws, not knowing first causes: from Science comes Prevision; from Prevision comes Action.

Why

Our direct means of acting are weak; knowing laws lets us predict, and predicting lets us change phenomena to our advantage.

In short

"Know to foresee, foresee to act" is an argument by Auguste Comte (Course of Positive Philosophy, 2nd lesson (1830) and 1st lesson) on the question "Can we be certain of anything?" (answer: through experience, with care). Its claim: Acting effectively requires foreseeing from observed laws, not knowing first causes: from Science comes Prevision; from Prevision comes Action. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P5). AskPhilosophy presents 3 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

Course of Positive Philosophy, 2nd lesson (1830) and 1st lesson

Valid with an implicit premise

What is science for? For Comte, to give us a power our body lacks. Our hands are weak, but if we know how phenomena follow one another, a small push at the right moment is enough to change the result. A meteorologist does not make rain, but he knows when it comes. This idea has a surprising consequence: if science serves to foresee and act, it has no need to look for "first causes" or the essence of things. Its laws are enough. But Comte adds that science should not be pursued only for its usefulness, and that pure theory has a dignity of its own.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.

Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P5, the computer finds a case where one acts effectively, foreseeing from laws, without those laws coming from observation: for example laws discovered by pure reasoning, such as mathematics applied to the sky before any measurement. That is exactly what P5 rules out.

With P5, the argument is valid. P1: acting on a large scale means modifying circumstances. P2: that means knowing the laws. P3: knowing the laws is foreseeing. P4: this knowledge does not seek first causes. P5: it comes only from observation. Five steps, one chain. Critics mostly target P5 (all observation already assumes a theory) and P4 (science has often advanced by looking for what lies behind phenomena). Note also what the argument does not say: Comte himself writes (2nd lesson, §10) that science has a higher purpose than usefulness, that of satisfying our need to know the laws.

Analogy. A sailor does not know why the Moon exists, but he reads the tides in a table and leaves at the right moment. Comte says: science is that table. Aristotle would answer that the true scholar also knows why.

Objections

Each objection is a conversation: click to see who replies and where the debate stands.

Pierre Duhem, The Aim and Structure of Physical Theory 1906 · attacks premise 5

There is no "pure" observed fact. In a laboratory, every instrument reading already assumes theories (about the instrument, about light, about matter). A fact therefore never tests a single law: it tests a whole set of theories. Laws do not come from observation alone.

Comte replies

summary: their text is not yet in our corpus

Comte What Comte already said (1st lesson, §14)

Every positive theory must be founded on observations, but in order to observe, our mind needs some theory or other.

The debate goes on (our summary) Comte sees here a circle of the mind at its beginnings, which theology is said to have broken (§15). Duhem goes further: even a mature science remains caught in this circle, each measurement carrying theories within it. For Duhem, P5 must therefore be corrected: laws come from observation and theory together, and cannot be separated.

Jean Perrin, Atoms (and spectral analysis, Kirchhoff and Bunsen, 1859) 1913 · attacks premise 4

Science has often advanced by looking for what is hidden behind phenomena. In Atoms (1913), Perrin gathers concordant measurements, obtained by very different methods, which show that atoms exist. Before him, many scientists treated them as mere calculating tools. Modern physics is made of entities that are not directly observed. Saying science does not look for causes deprives it of its greatest discoveries.

no reply

summary: their text is not yet in our corpus

No reply possible: objection raised in 1913, after the author's death (1857).

The debate goes on (our summary) Comte died in 1857. He is mostly reproached for a sentence in lesson 19 (outside our corpus) which judged it impossible ever to know the chemical composition of the stars: the spectral analysis of Kirchhoff and Bunsen (1859) made it possible two years after his death. His defenders note that Comte only ruled out hypotheses that no observation can check. But scientists close to the positivist outlook, such as the chemist Marcellin Berthelot in France, long held atoms to be a useless hypothesis, and Perrin precisely turned that hypothesis into a measured fact.

Aristotle, Metaphysics 350 BC · attacks premise 4

For Aristotle, to know truly is to know through causes: whoever knows why a thing is so knows more than whoever knows only that it is so. Those who teach are those who tell the causes of each thing. A science that gives up the why gives up knowledge itself.

Comte replies

Comte What Comte says about the search for causes (1st lesson, §23)

In our positive explanations, even when they are most complete, we do not pretend to explain the real causes of phenomena, as this would merely throw the difficulty further back.

The debate goes on (our summary) Comte does not answer Aristotle by name: his text sets aside first and final causes, not all explanation. Aristotle would answer that a chain of causes one climbs without end is not a reason to stop: it is a reason to look for a first cause (Metaphysics, A and alpha 2). Comte sees in this regress the proof that the question has no meaning; Aristotle sees in it the proof that it has one.