Extending knowledge by investigating things

Zhu Xi 1130 · 1200Study the principle (li) of things to perfect oneself.

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What it claims

Whoever patiently pursues the study of things can reach real, overall knowledge, without having known everything.

Why

Everything has its principle and the mind is made to know it: after long study, understanding opens all at once.

In short

"Extending knowledge by investigating things" is an argument by Zhu Xi (Great Learning, added chapter; Classified Conversations 18) on the question "Can we be certain of anything?" (answer: yes, through reason). Its claim: Whoever patiently pursues the study of things can reach real, overall knowledge, without having known everything. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 3 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

Great Learning, added chapter; Classified Conversations 18

Valid with an implicit premise

How can we reach sure knowledge, above all about how to live well? The Great Learning says: "extending knowledge lies in investigating things". The commentary on this passage was lost: Zhu Xi wrote it himself, saying he took up Cheng Yi's idea. His answer: every thing has its principle and the mind is made to know; so one must study things one by one, starting from what one already knows, without claiming to exhaust them all, until the day understanding opens up all at once. The P1..P3 → C form is our reconstruction and simplifies: for him this knowledge serves right action, and goes with an attentive mind. The camp "Yes, through reason" is the closest, without being exact: this knowledge passes through the examination of things (experience), and Zhu Xi does not say certainty is immediate. The camp "through experience, with care" fits less, since he judges that an overall knowledge is attainable.

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 P4, the computer finds a case where someone studies for a long time and feels that everything connects, yet does not have real knowledge: an illusion of the whole, like believing one understands a language one only recognises.

The argument is valid and its four premises are essential. The weak point is P4, which the text does not demonstrate: it asserts that the sudden understanding is true, and his critics ask how to check this. Zhu Xi answers in practice: whoever really knows no longer does the opposite (as one does not eat what one knows to be poison). Another weakness: P2 is a promise about the future, which only each person's experience can confirm. The argument is not about science in the modern sense: "the principles" are first those of conduct, ritual and history.

Analogy. Learning a city by walking it: at first you know separate streets, then one day the map forms all at once. You do not need to have seen every house to find your way.

Objections

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

A student (Classified Conversations) attacks premise 2

Investigating things is the hardest of tasks. How can one investigate them all?

Zhu Xi replies

Zhu Xi

Cheng Yi does not say that after examining one thing you understand everything, nor that you understand only after examining them all. He only says that, when the accumulation is great, you suddenly reach a point where everything connects.

Zhu Xi (another conversation)

If eight or nine things out of ten have been studied, the remaining one or two, even unstudied, will become clear by themselves when everything comes together.

The debate goes on (our summary) The answer shifts the difficulty more than it removes it: how do we know we have accumulated enough, and that the remaining things are of the same kind? Elsewhere Zhu Xi specifies that this does not mean knowing everything (Yulei 18, §21). (Our summary.)

Lu Jiuyuan (as summarised by a student of Zhu Xi) 1175 · attacks premise 2

Lu does not accept Cheng Yi's thesis on investigating things. If one discusses affairs one by one, the mind wears out. Better to look into one's own mind: when it is clear, it lights up everything, and it is less laborious.

Zhu Xi replies

Zhu Xi

If one does not discuss each affair, one lets anything happen: the mouth says what comes, the feet go where they like, one moves in the dark without caring about anything.

Zhu Xi (another conversation, on Lu Zijing)

Lu says for example "innate knowledge and ability, the four sprouts have their roots in the heart": he is only playing with this thing. The other things that should be studied, he cannot deal with, and he forbids others to study them.

The debate goes on (our summary) The text we have is by a student of Zhu Xi: Lu's own words are not in our corpus. According to the history of thought, Lu held that "the mind is principle": the principle is already in us, and study serves to bring it out, not to look for it outside. The Goose Lake debate (1175), organised by Lü Zuqian, did not bring them to agreement. (Our summary.)

Wang Yangming 1492 · attacks premise 2

In his youth (around 1492), Wang Yangming tried, with a friend, to investigate the bamboos in the garden to grasp their principle, day and night. The friend fell ill on the third day, he himself on the seventh, understanding nothing. He concluded that this method does not lead to wisdom, and that the principle is in the mind, not in outside things. (Story recorded by his students in the Instructions for Practical Living, published in full in 1556, after his death.)

no reply

summary: their text is not yet in our corpus

No reply possible: objection raised in 1492, after the author's death (1200).

The debate goes on (our summary) A defender of Zhu Xi would answer that he does not ask to stare at an object: he says to start from what is near, one thing after another (Yulei 18, §41), and he himself judges that studying each blade of grass and each tree one by one, day after day, would be endlessly tedious (Yulei 18, §22). Wang Yangming would retort that even so, knowledge is separated from the mind. (Our summary.)