In oracle bone and bronze script, 以 shows a person (人) carrying or leading something — the act of taking by hand, guiding forward, employing. The core sense is to use, to take, to employ. The Shuōwén Jiězì defines 以 as 用也 — "to use."

As a preposition, 以 marks the instrument or means by which an action is carried out: 以刀切 (cut with a knife), 以德报怨 (repay with virtue). As a conjunction, it marks purpose or cause: 以防万一 (in order to guard against any eventuality). Both functions descend directly from the root sense of "employing" one thing in the service of another.

In modern Mandarin, 以 has retreated significantly into formal and written registers. Colloquial speech replaces most 以 + verb constructions with 用 (to use), 因为 (because), or 为了 (in order to). But 以 persists — embedded in dozens of fixed compounds, in classical quotation, and in the formal prose of newspapers, law, and academia.

The most productive classical pattern using 以 is 以 X 为 Y — "to take X as Y; to treat X as Y; to regard X as Y; to use X in the role of Y." This construction is the engine of classical Chinese argument, the standard way of asserting a standard or a valuation.

以天下为己任 yǐ tiānxià wéi jǐ rèn — to take all under heaven as one personal responsibility. The defining aspiration of the Confucian public servant: the world is not someone else's problem.

以和为贵 yǐ hé wéi guì — to take harmony as the highest value. From the Analects I.12 (有子): 礼之用，和为贵 — "In the application of ritual, harmony is what matters most." The most cited Confucian statement on why social harmony is the end toward which ritual points.

以德报怨 yǐ dé bào yuàn — to repay resentment with virtue. This phrase crosses Laozi and the Analects. Confucius in the Analects (XIV.36) responds with characteristic concreteness: "What then would you use to repay virtue? Repay resentment with uprightness (以直报怨), and repay virtue with virtue." A direct, contested ethical position, not a simple endorsement of unlimited forgiveness.

以人为本 yǐ rén wéi běn — to take the human as the root and foundation. Central to modern Chinese social policy framing, the phrase has deep classical roots: the Guanzi reads 夫霸王之所始也，以人为本 — "The beginning of kingship lies in taking the people as the root."

以 + noun phrase = by means of / using / with. This is 以 marking the instrument or method: 以笔为剑 (using the brush as a sword), 以理服人 (to convince people by means of reason). In classical texts this construction appears constantly. In modern formal writing it persists for rhetorical weight: 以实际行动证明 (to prove through practical action).

以 + verb phrase = in order to / so as to. Here 以 marks purpose — what the action is aimed at achieving. This is the source of the productive set of 以 + verb compounds in modern Chinese: 以免 (in order to avoid), 以便 (in order to facilitate), 以防 (as a precaution against). These three are fully modern and appear in ordinary written language.

In classical Chinese (文言文), 以 has a wider and more syntactically flexible role than in modern speech. Several patterns appear repeatedly in canonical texts:

以…故 yǐ…gù — "because of; for the reason of." A common causal connector in classical prose: 以此故 (for this reason), 以贫故不仕 (because of poverty, one did not take office). In modern Chinese, 因此 and 所以 cover this ground.

Sentence-final and medial 以 marking means just used. In Mencius: 申之以孝悌之义 — "Instilling in them the principles of filial piety and brotherly respect [by these means]." The 以 phrase comes after the main verb, specifying the instrument of the action. This post-verbal position is a classical feature that modern Chinese inverts: means phrases now precede the verb.

以此 yǐ cǐ — "by means of this; therefore" — a formal connector drawing a consequence from what was just stated.

Classical proverb structure: 以 X 喻 Y — to use X as an illustration of Y. The standard formula for analogy in classical argument.

The Analects compound 一言以蔽之 yī yán yǐ bì zhī — "to cover it all with one word; to sum up in a phrase" — preserves the classical 以 + verb structure intact and is still used in modern formal writing as a rhetorical opener.

Picture 以 as a hand extended outward, offering one thing in service of another. That gesture — "here, use this" — is the root of everything 以 does. When 以 precedes a noun it says: "here is the instrument." When 以 precedes a verb phrase it says: "here is the purpose." When 以 anchors 以…为 it says: "take this, treat it as that."

The three chengyu that carry 以 deepest into Chinese civilization all share this logic. 以身作则: here is the whole self, offered as the standard. 以德报怨: here is virtue, offered in return for resentment. 以和为贵: here is harmony, elevated into what is held precious. One character, one gesture, centuries of ethical argument.