QuestionsCan we be certain of anything?Judging a report by the nature of things
Can we be certain of anything?Through experience, with care

Judging a report by the nature of things

The critique of historians

Ibn Khaldun 1332 · 1406Civilisations rise and fall with the strength of their solidarity.
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What it claims

A report must first be judged by its agreement with the nature of society, known through observation. For example, no kingdom can support more soldiers than its resources allow: Moses did not count 600,000 fighters.

Why

An impossible story is not made credible by honest witnesses: it must be checked against how society actually works.

In short

"Judging a report by the nature of things" is an argument by Ibn Khaldun (Muqaddima, Introduction and Book One, preliminary remarks) on the question "Can we be certain of anything?" (answer: through experience, with care). Its claim: A report must first be judged by its agreement with the nature of society, known through observation. For example, no kingdom can support more soldiers than its resources allow: Moses did not count 600,000 fighters. 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.

Muqaddima, Introduction and Book One, preliminary remarks
Valid with an implicit premise

The great historians of his time report that Moses counted more than 600,000 soldiers, that Alexander went down to the bottom of the sea in a glass box, that there is a city made entirely of copper in the desert. Muslim scholars usually judged a report by those who had handed it down: were they honest, accurate? Ibn Khaldun proposes a stronger criterion: first ask whether what is reported is possible, by comparing it with what we observe today. A kingdom cannot support more soldiers than its resources allow; contemporaries themselves inflate figures tenfold. He believes he holds a "demonstrative" method. His criterion is that of experience: the past is judged by the present.

P1Historical reports are naturally prone to falsehood: partisanship, blind trust in those who hand them down, flattery of the powerful, a taste for the extraordinary. A criterion is needed to sort them.
P2Checking the honesty of those who hand reports down is not enough: if what is reported is impossible, there is no point asking whether the witness is trustworthy.
P3Human society has a nature: some things follow from it necessarily, others happen by accident, others are impossible. Whoever knows this nature can sort true from false.
P4This nature is known by comparing what is reported with what we observe, the past with the present: "the past resembles the future more than one drop of water another".
P5 · implicit premiseTo judge a report about the past, there are only two means: trusting those who handed it down, or testing it against the nature of things.
Therefore a report must first be judged by its agreement with the nature of society, known through observation. For example, no kingdom can support more soldiers than its resources allow: Moses did not count 600,000 fighters.

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 a criterion is needed, where witnesses are not enough, where the nature of things is known, and where the right criterion is nonetheless a third one: for example a contemporary document or an excavation.
With P5, the argument is valid: a criterion is needed (P1), trust in witnesses is not enough (P2), so, if there are only two criteria (P5), one must turn to the nature of things, which can be known (P3, P4). P5 is implicit: Ibn Khaldun only contrasts the criticism of witnesses with the examination of what is possible. This is the point historians discuss today: they also have archives, inscriptions, coins, archaeological digs.
Analogy. A friend tells you a cousin ran the hundred metres in five seconds. No need to ask whether your friend is honest or the cousin reliable: you know no human runs that fast. The report falls before any inquiry into the witnesses.

Objections

3

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

A difficulty Ibn Khaldun sees himself attacks premise 4

The past does not always resemble the present: customs, regimes and techniques change. Judging the ancients by what we see today risks taking for impossible what was merely different.

Ibn Khaldoun replies
summary: their text is not yet in our corpus
Ibn Khaldoun
It is a hidden error of historians to forget that the condition of nations and peoples changes with the passing of periods. This affliction is hard to see, because it becomes noticeable only after long periods.
The debate goes on (our summary) So Ibn Khaldun acknowledges change, and warns against anachronism. His solution lies in his rule: distinguish what belongs to the nature of every society (a kingdom needs resources to pay its soldiers) from what is accidental and changes (customs, languages, regimes). The whole difficulty is knowing, in a given case, on which side of the line one stands. (Our summary.)
M
Modern historians attacks premise 3

What he calls "the nature of things" is often the science of his time. To refute Alexander's dive, his "most evident" argument is that hot air upsets the humours of the lung; he explains the merriness of the Egyptians and the gloom of the people of Fez by the heat or cold of the air. A criterion of the possible is only as good as the science that sets it.

no reply
No reply possible: objection raised after the author's death (1406).
The debate goes on (our summary) The criticism is fair for his examples: diving bells can be built today, and explaining character by climate has been abandoned, as have his judgements on the peoples of hot countries. But it does not destroy the method: historians still reject a report that contradicts what is known; it is simply that knowledge has changed. (Our summary.)
C
Critical readers attacks premise 2

He does not apply his criterion everywhere. For the Israelites, he grants that a multiplication contrary to experience may have happened by miracle. He keeps the criticism of witnesses for religious reports. And he rejects the report of a caliph drinking wine because that caliph was pious: this is the partisanship he denounces in others.

Ibn Khaldoun replies
Ibn Khaldoun
If the criticism of witnesses is kept for reports of religious law, it is because most of them are injunctions: the law only asks that they be presumed true, and this presumption comes from the honesty and accuracy of those who hand them down. Reports of facts must, in addition, agree with reality.
The debate goes on (our summary) This answer justifies the different treatment of hadiths, which say what must be done. It covers neither the miracle, which is a report of fact, nor the caliph Harun al-Rashid. For the latter, Ibn Khaldun also gives historical reasons (the fall of the Barmakids is explained by a power struggle), but the weight he gives to the caliph's piety shows that his own criterion is not always applied impartially. (Our summary.)