"The contract was signed BY the CEO" = BY + agent (the person who signs). "The document was signed WITH a digital pen" = WITH + instrument (the tool used to sign). BY = who did it. WITH = what it was done with. "The letter was written BY the director" (agent = director). "The letter was written WITH a fountain pen" (instrument = fountain pen).
BY + AGENT IN PASSIVE VOICE: introduces the AGENT — the person, organization, or force that performs the action. "The report was written BY the research team" (who wrote it). "The decision was made BY the board." "The building was designed BY a Spanish architect." THE AGENT IS AN ACTING ENTITY: BY generally introduces an entity that performs the action intentionally or is the primary causal source. "The city was destroyed BY the earthquake" (the causative natural force). "The patient was treated BY a specialist." HOW MANY PASSIVES INCLUDE BY: statistically, only about 20% of passive constructions in real English include an agent with BY. Most passives omit the agent ("The report was approved" without BY). WHEN BY IS INCLUDED: when the agent is NEW OR IMPORTANT information that the listener/reader does not know. "The article was published BY The Economist."
The internal investigation was led BY an independent panel of external experts appointed specifically to ensure that the review process was conducted with full impartiality and without any conflict of interest.
The proposed amendment was rejected BY a majority of the committee members at the second reading, on the grounds that it failed to adequately address the concerns that had been raised during the public consultation process.
The acquisition was structured BY the legal and financial advisory teams over a period of several months and was ultimately approved BY the relevant competition authorities in both the target and acquiring companies' home jurisdictions.
WITH + INSTRUMENT IN PASSIVE VOICE: introduces the INSTRUMENT, TOOL, or MEANS used to perform the action. The instrument is not the agent — it is what the agent USES to carry out the action. "The letter was signed WITH a pen" (instrument = pen; the real agent is the person using it). "The window was broken WITH a stone." "The data was analysed WITH specialist software." DIFFERENCE WITH BY: "The window was broken BY a child" (agent: the child — who did it). "The window was broken WITH a stone" (instrument: the stone — what was used). THEY CAN CO-EXIST: "The window was broken BY the child WITH a stone" = the child (agent, BY) used a stone (instrument, WITH). OTHER INSTRUMENT PREPOSITIONS: IN + material (written/made WITH): "written IN ink / sculpted IN marble." THROUGH + indirect means: "communicated THROUGH official channels."
The data room was secured WITH advanced encryption protocols and multi-factor authentication requirements, ensuring that only pre-authorized participants in the due diligence process could access the sensitive transaction documentation.
The structural components were joined WITH a specialist high-temperature adhesive compound specifically developed for aerospace applications, replacing the welding technique that had been used in the previous generation of the product.
The boundaries of the disputed territory have been demarcated WITH a series of GPS-verified markers installed at precisely calculated intervals under the terms of the bilateral agreement signed by both parties at the conclusion of the mediation process.
Common mistake
THE TYPICAL ERROR: confusing the agent (BY) with the instrument (WITH). "The report was written WITH the manager" = INCORRECT (the manager is not an instrument — they are an acting person = BY). "The report was written BY the manager" = CORRECT. "The data was analysed BY specialist software" = debatable (software does not act intentionally — it is an instrument; however, in modern English, BY is increasingly accepted for software/technological tools). "The report was written BY a pen" = INCORRECT (a pen does not act — it is an instrument = WITH). TEST: Who acted/made the decision? = BY. With what tool/material? = WITH. SPECIAL CASE: when a natural force acts as agent, BY is correct: "destroyed BY fire / BY the storm / BY the virus." When speaking about material: "built WITH concrete / filled WITH water."
Trick to remember it
ASK FOR THE ACTIVE SUBJECT: "Who/What did it?" If the answer is a PERSON or ORGANIZATION acting = BY. If the answer is a TOOL or MATERIAL used = WITH. "The door was opened" — who opened it? If a person: "by the security guard." With what? If a key: "with a key." BOTH: "The door was opened BY the security guard WITH a master key." BOTH CAN APPEAR TOGETHER, BY before WITH.
Quick rule
BY + AGENT = person/entity/force performing the action ("by the manager / by the storm"). WITH + INSTRUMENT = tool/material/means used ("with a pen / with special software"). They can coexist: "written BY the director WITH a fountain pen." Person/actor = BY. Tool used = WITH.
Did you know?
The BY (agent) vs WITH (instrument) distinction in the passive voice reflects one of the most universal semantic categories of human language: the distinction between AGENT (the one who acts with intention or will) and PATIENT or INSTRUMENT (what receives the action or is used to perform it). Case Grammarians (Case Grammar, developed by Charles Fillmore in the 1960s) identified these categories as universal semantic primitives — present in all languages, though with different morphological markers. In Latin, the distinction was marked with different cases: the agent went in ablative with "a/ab" and the instrument went in the instrumental ablative without preposition. Modern English uses BY and WITH. What is fascinating is that this distinction between agent and instrument is so fundamental to human cognition that it appears even in questions: "Who (agent) broke the window?" vs "What (instrument/object) was used to break the window?"
Exercise 1 · Pick the right one
The merger agreement was negotiated _____ a team of senior partners from three different law firms, and the final documents were signed _____ a secure digital signature platform that meets the applicable e-signature regulatory standards.
Exercise 2 · Pick the right one
The historical archives were damaged _____ the flood that struck the city in 1987, and several of the most important documents had to be painstakingly restored _____ a specialist conservation team using traditional techniques.
Exercise 3 · Form the word
BY + AGENT = person/entity/force performing the action ("by the manager / by the storm"). WITH + INSTRUMENT = tool/material/means used ("with a pen / with special software"). They can coexist: "written BY the director WITH a fountain pen." Person/actor = BY. Tool used = WITH.
THE TYPICAL ERROR: confusing the agent (BY) with the instrument (WITH). "The report was written WITH the manager" = INCORRECT (the manager is not an instrument — they are an acting person = BY). "The report was written BY the manager" = CORRECT. "The data was analysed BY specialist software" = debatable (software does not act intentionally — it is an instrument; however, in modern English, BY is increasingly accepted for software/technological tools). "The report was written BY a pen" = INCORRECT (a pen does not act — it is an instrument = WITH). TEST: Who acted/made the decision? = BY. With what tool/material? = WITH. SPECIAL CASE: when a natural force acts as agent, BY is correct: "destroyed BY fire / BY the storm / BY the virus." When speaking about material: "built WITH concrete / filled WITH water."
ASK FOR THE ACTIVE SUBJECT: "Who/What did it?" If the answer is a PERSON or ORGANIZATION acting = BY. If the answer is a TOOL or MATERIAL used = WITH. "The door was opened" — who opened it? If a person: "by the security guard." With what? If a key: "with a key." BOTH: "The door was opened BY the security guard WITH a master key." BOTH CAN APPEAR TOGETHER, BY before WITH.
Bryan López
Founder of SpeakUP Academy