二人同心，其利断金

Two people share an intention. They want the same thing. They want it for the same reasons. They are willing to do the work.

The I Ching’s image: their union is a blade. The blade can cut through gold.

This is the power of true partnership. Two people of one heart are stronger than any single person, and stronger than any committee.

The Characters

• 二 (èr): Two
• 人 (rén): People, persons
• 同 (tóng): Same, shared
• 心 (xīn): Heart, mind, intention
• 其 (qí): Their
• 利 (lì): Sharpness (here: as a noun, “their sharpness”)
• 断 (duàn): Cut, sever
• 金 (jīn): Gold, metal

二人同心，其利断金, “two-people same-heart, their sharpness cuts-gold.” Two parallel clauses. The first names the condition. The second names the consequence.

The image of 金 (gold) is significant. Gold is the most resistant material. To say their sharpness cuts gold is to say nothing can resist them.

Where It Comes From

The I Ching (易传, 系辞上, ‘Appended Remarks, Part I’), Chapter 8, the full passage:

The context is the I Ching’s commentary on Hexagram 13, 同人 (Tong Ren, “Fellowship with Men”). The hexagram is about the power of true human partnership. The commentary elaborates:

「同人，先号咷而后笑。」子曰：「君子之道，或出或处，或默或语。二人同心，其利断金。同心之言，其臭如兰。」

“The hexagram Tong Ren says: ‘First they weep aloud, then they laugh.’ The Master said: The way of the noble person, whether going forth or staying at home, whether silent or speaking: when two people share one heart, their sharpness cuts through gold. Words spoken from a shared heart are fragrant as orchids.”

The line sits in a passage about the depth of true fellowship. The path is sometimes hard (the weeping). The culmination is the joy of partnership (the laughter). And the engine is the shared heart, which produces both the cutting power and the fragrance.

The Philosophy

The power of shared intention.

The line’s first claim: shared intention multiplies force. Two people working toward the same goal are not twice as effective as one. They are many times as effective. The multiplication comes from removing the friction of disagreement, misalignment, and unspoken resentment.

This is observable in any domain. The marriage that has worked through its disagreements is more powerful than either spouse alone. The founding team that has aligned on the mission can do what no individual founder could. The sports team that has bought into the system plays above its talent. The military unit that has trained together is unbeatable by a larger but less cohesive unit.

The rarity of true partnership.

The line implies that this rarity is the difficulty. Most partnerships are not of one heart. The marriage that is, is precious. The founding team that is, is precious. The friendship that is, is precious.

The line names the achievement. It does not name the cost. The cost is years of work: the difficult conversations, the shared failures, the moments of doubt, the repair of betrayals large and small. Two people of one heart have typically earned it.

The complement: words like orchids.

The closing line of the passage, 同心之言，其臭如兰 (“words spoken from a shared heart are fragrant as orchids”), is the complement. True partnership produces a particular quality of communication: the words that pass between two people of one heart have a fragrance, a quality of rightness.

The orchid image is specific. The orchid is the Chinese flower of subtle, refined beauty. It does not announce itself. It is noticed by those who attend. The communication of true partnership has this quality: not loud, but unmistakable to those who notice.

Where this shows up today:

• The co-founder relationship. The two founders who share a mission and a method, and who have worked through their differences. The partnership that allows the company to weather any storm.
• The marriage. The two spouses who have aligned on what they want from life, and who have done the work of staying aligned through changes.
• The creative partnership. The writer-editor, director-actor, composer-librettist pairs who complete each other’s work. The McCartney-Lennon, Wordsworth-Coleridge, Gilbert-Sullivan version of the image.
• The sports duo. The point guard and center who can read each other without looking. The tennis doubles pair that moves as one.
• The military unit. The squad that has trained together so long that each member can predict the others’ moves. The squad that survives by doing so.
• The research partnership. The two scientists who think together so well that neither can fully tell which ideas were whose.
• The friendship. The friend with whom one has nothing to hide. The conversation that picks up where it left off, even after years apart.

Cross-cultural parallels:

• Ecclesiastes 4:9-12. “Two are better than one, because they have a good reward for their toil. For if they fall, one will lift up his fellow. … And though a man might prevail against one who is alone, two will withstand him; a threefold cord is not quickly broken.” The Judeo-Christian parallel.
• The Greek myth of Damon and Pythias. The friendship so deep that each will die for the other. The Western mythic articulation.
• Aristotle, Nicomachean Ethics (Books 8-9). The treatise on friendship. The Greek philosophical parallel.
• The English idiom “thick as thieves.” The colloquial articulation of two people so closely aligned they seem to share one mind.
• The military doctrine of “unit cohesion.” The recognition that the small unit that has trained together is the foundation of military effectiveness.
• The Japanese business concept of 絆 (kizuna, the bond). The recognition that the relationship between two people who have aligned is itself a form of capital.

When Chinese Speakers Use It

Scenario 1: Naming a marriage

A friend describing her parents’ marriage: “二人同心，其利断金. Sixty years. They had one heart. Nothing could break it.”

Scenario 2: Naming a founding team

A journalist describing a successful startup: “二人同心，其利断金. The two founders finished each other’s sentences. That is what carried them through the dark years.”

Scenario 3: Naming a friendship

A friend describing her closest friend: “二人同心. We have not spoken in two years. We will pick up where we left off.”

Scenario 4: Self-counsel

A founder reflecting on her co-founder: “二人同心，其利断金. We are not yet of one heart. The work to get there is the most important work I can do.”

Cultural Notes

二人同心，其利断金 is taught in school and used constantly in discussions of marriage, partnership, and friendship. It is one of the most commonly quoted lines at Chinese weddings.

For 2,000 years, the line has anchored the Chinese praise of true partnership. The marriage that has been worked at. The founding team that has aligned. The friendship that has been tested and survived.

The line is paired with 同人卦 (Hexagram 13 of the I Ching, “Fellowship with Men”) and with the broader Confucian emphasis on 友 (friendship) and 信 (trust). Together they form the I Ching-Confucian cluster on the power of shared intention.

A common misread: the line is not saying that any two people who work together can cut gold. It is saying that two people of one heart can. The “one heart” is the achievement. Most partnerships do not get there.

Tattoo Advice

二人同心 works as a marker of partnership: I am one half of a shared heart. The work to keep our hearts aligned is the most important work I do.

Length and placement:

• 4-character compression 二人同心: wrist, ankle, sternum, behind ear
• 8 characters full 二人同心其利断金: forearm (vertical), upper arm, ribcage

Pairings:

• 君子和而不同 (Analects 13.23) for the Confucian partnership cluster
• 有朋自远方来不亦乐乎 (Analects 1.1) for the Confucian friendship cluster
• 德不孤必有邻 (Analects 4.25) for the same cluster

Calligraphy style: Elegant semi-cursive (行书). The line is warm and a little celebratory; the calligraphy should feel open.

Best audience: A founder, spouse, partner, or close friend whose life has been transformed by a true partnership.