four eyes principle

The four eyes principle is a requirement that two individuals approve some action before it can be taken. The four eyes principle is sometimes called the two-man rule or the two-person rule.

In a business context, the four eyes required for approval are often those of the CEO (Chief Executive Officer) and the CFO (Chief Financial Officer), who must both sign off on any significant business decision. In editing, proofreading and translation,  documents typically have a second reader to detect errors and typos that a single pair of eyes might miss. Although neither individual might detect all errors, two readers are likely to miss different things so that, collaboratively, they will catch more mistakes.

Here are a few other examples of the four eyes principle at work:

• Many legal and financial documents require the signatures of two individuals.
• Banks, casinos and sensitive military areas often include no-lone zones: areas in which two people must be present and within each other's line of vision at all times.
• The Emergency War Orders (EWO) safe, which contains missile launch keys and codes, is locked by two padlocks with keys held by different launch officers.
• Some data management systems require that important record updates be approved by two separate people before the data is committed.

Although the four eyes principle adds an element of security to any decision-making process, its effectiveness relies upon the ability, integrity and diligence of the individuals involved. In a refinement of the basic principle, a random rotation of authorized individuals serves as the second pair of eyes, so that it cannot be known with any certainty which two individuals will be dealing with a given decision.