Consensus decision-making is a group decision-making process in which group members develop, and agree to support a decision in the best interest of the whole. Consensus may be defined professionally as an acceptable resolution, one that can be supported, even if not the "favourite" of each individual. Consensus is defined by Merriam-Webster as, first, general agreement, and second, group solidarity of belief or sentiment. It has its origin in the Latin word cōnsēnsus (agreement), which is from cōnsentiō meaning literally feel together .  It is used to describe both the decision and the process of reaching a decision. Consensus decision-making is thus concerned with the process of deliberating and finalizing a decision, and the social, economic, legal, environmental and political effects of applying this process.
As a decision-making process, consensus decision-making aims to be: 
- Agreement Seeking: A consensus decision-making process attempts to generate as much agreement as possible. 
- Collaborative: Participants contribute to a shared proposal and shape it into a decision that meets the concerns of all group members as much as possible.
- Cooperative: Participants in an effective consensus process should strive to reach the best possible decision for the group and all of its members, rather than competing for personal preferences.
- Egalitarian: All members of a consensus decision-making body should be afforded, as much as possible, equal input into the process. All members have the opportunity to present, and amend proposals.
- Inclusive: As many stakeholders as possible should be involved in the consensus decision-making process.
- Participatory: The consensus process should actively solicit the input and participation of all decision-makers. 
Alternative to common decision-making practices
Consensus decision-making is an alternative to commonly practiced group decision-making processes.  Robert's Rules of Order , for instance, is a guide book used by many organizations. This book allows the structuring of debate and passage of proposals that can be approved through majority vote. It does not emphasize the goal of full agreement. Critics of such a process believe that it can involve adversarial debate and the formation of competing factions. These dynamics may harm group member relationships and undermine the ability of a group to cooperatively implement a contentious decision. Consensus decision-making attempts to address the beliefs of such problems. Proponents claim that outcomes of the consensus process include: 
- Better decisions: Through including the input of all stakeholders the resulting proposals may better address all potential concerns.
- Better implementation: A process that includes and respects all parties, and generates as much agreement as possible sets the stage for greater cooperation in implementing the resulting decisions.
- Better group relationships: A cooperative, collaborative group atmosphere can foster greater group cohesion and interpersonal connection.
The level of agreement necessary to finalize a decision is known as a decision rule. Possible decision rules for consensus vary within the following range:
- Unanimous agreement
- Unanimous consent (See agreement vs consent below)
- Unanimous agreement minus one vote or two votes
- Unanimous consent minus one vote or two votes
- Condorcet consensus
- Super majority thresholds (90%, 80%, 75%, two-thirds, and 60% are common).
- Simple majority
- Executive committee decides
- Person-in-charge decides
In groups that require unanimous agreement or consent (unanimity) to approve group decisions, if any participant objects, they can block consensus according to the guidelines described below. These groups use the term consensus to denote both the discussion process and the decision rule. Other groups use a consensus process to generate as much agreement as possible, but allow participants to finalize decisions with a decision rule that does not require unanimity. In this case, someone who has a strong objection must live with the decision.
Agreement vs. consent
Giving consent does not necessarily mean that the proposal being considered is one’s first choice. Group members can vote their consent to a proposal because they choose to cooperate with the direction of the group, rather than insist on their personal preference. Sometimes the vote on a proposal is framed, “Is this proposal something you can live with?” This relaxed threshold for a yes vote can achieve full consent. This full consent, however, does not mean that everyone is in full agreement. Consent must be 'genuine and cannot be obtained by force, duress or fraud.' The values of consensus are also not realized if "consent" is given because participants are frustrated with the process and wanting to move on.
Furthermore, consent, as within Sociocracy, is defined simply by the absence of reasonable objections. An objection is a reason why doing what is proposed stands in the way of satisfying needs or goals, which the proposal aims to satisfy. Consent deliberately seeks objections, which reveal wisdom that can be used to improve proposals and agreements.
Healthy consensus decision-making processes usually encourage expression of dissent early, maximizing the chance of accommodating the views of all minorities. Since unanimity may be difficult to achieve, especially in large groups, or consent may be the result of coercion, fear, undue persuasive power or eloquence, inability to comprehend alternatives, or plain impatience with the process of debate, consensus decision-making bodies may use an alternative decision rule, such as Unanimity Minus One (or U−1), or Unanimity Minus Two (or U−2).
Condorcet consensus is defined as the decision which is the Condorcet winner as in Condorcet method. The Condorcet consensus does not require unanimous or near-unanimous consensus - which cannot be realistically reached in big group sizes - but maximizes satisfaction rate. It can also be argued that when a Condorcet consensus is reached, further deliberation will only strengthen and further specify this consensus.
Combined with majority or super-majority decision rules
A consensus process can also be concluded with a majority or super-majority vote. This is especially common or useful in large and diverse groups that share the values underlying consensus. Consensus process, by definition, seeks the maximum possible levels of agreement or consent. Thus, if a group using a majority vote decision rule is dominated by a majority faction that does not seek the agreement of all participants, the process would not be considered "consensus." Regardless of the decision rule, the process is only "consensus" if it has embodied the value of striving for full agreement or consent. Sometimes the outcomes of consensus can be contrary to majority.
Blocking and other forms of dissent
To ensure the agreement or consent of all participants is valued, many groups choose unanimity or near-unanimity as their decision rule. Groups that require unanimity allow individual participants the option of blocking a group decision. This provision motivates a group to make sure that all group members consent to any new proposal before it is adopted. Proper guidelines for the use of this option, however, are important. The ethics of consensus decision-making encourage participants to place the good of the whole group above their own individual preferences. When there is potential for a block to a group decision, both the group and dissenters in the group are encouraged to collaborate until agreement can be reached. Simply vetoing a decision is not considered a responsible use of consensus blocking. Some common guidelines for the use of consensus blocking include:
- Limiting the allowable rationale for blocking to issues that are fundamental to the group’s mission or potentially disastrous to the group.
- Limiting the option of blocking to decisions that are substantial to the mission or operation of the group and not allowing blocking on routine decisions.
- Providing an option for those who do not support a proposal to “stand aside” rather than block.
- Requiring a block from two or more people to put a proposal aside.
- Requiring the blocking party to supply an alternative proposal or a process for generating one.
- Limiting each person’s option to block consensus to a handful of times in one’s life.
When a participant does not support a proposal, he or she does not necessarily need to block it. When a call for consensus on a motion is made, a dissenting delegate has one of three options:
- Declare reservations: Group members who are willing to let a motion pass but desire to register their concerns with the group may choose "declare reservations." If there are significant reservations about a motion, the decision-making body may choose to modify or re-word the proposal. 
- Stand aside: A "stand aside" may be registered by a group member who has a "serious personal disagreement" with a proposal, but is willing to let the motion pass. Although stand asides do not halt a motion, it is often regarded as a strong "nay vote" and the concerns of group members standing aside are usually addressed by modifications to the proposal. Stand asides may also be registered by users who feel they are incapable of adequately understanding or participating in the proposal.   
- Object: Any group member may "object" to a proposal. In groups with a unanimity decision rule, a single block is sufficient to stop a proposal. Other decision rules may require more than one objection for a proposal to be blocked or not pass (see previous section, Decision rules ).
Blocks are generally considered an extreme measure—only used when a member feels a proposal endangers the organization or its participants, or violates the mission of the organization (i.e., a principled objection). In some consensus models, a group member opposing a proposal must work with its proponents to find a solution that works for everyone. 
There are multiple stepwise models of how to make decisions by consensus. They vary in the amount of detail the steps describe. They also vary depending on how decisions are finalized. The basic model involves
- collaboratively generating a proposal,
- identifying unsatisfied concerns, and then
- modifying the proposal to generate as much agreement as possible.
After a concerted attempt at generating full agreement, the group can then apply its final decision rule to determine if the existing level of agreement is sufficient to finalize a decision.
In the spokescouncil model, affinity groups make joint decisions by each designating a speaker and sitting behind that circle of spokespeople, akin to the spokes of a wheel. While speaking rights might be limited to each group's designee, the meeting may allot breakout time for the constituent groups to discuss an issue and return to the circle via their spokesperson. In the case of an activist spokescouncil preparing for the A16 Washington D.C. protests in 2000, affinity groups disputed their spokescouncil's imposition of nonviolence in their action guidelines. They received the reprieve of letting groups self-organize their protests, and as the city's protest was subsequently divided into pie slices, each blockaded by an affinity group's choice of protest. Many of the participants learned about the spokescouncil model on the fly by participating in it directly, and came to better understand their planned action by hearing others' concerns and voicing their own. 
Once an agenda for discussion has been set and, optionally, the ground rules for the meeting have been agreed upon, each item of the agenda is addressed in turn. Typically, each decision arising from an agenda item follows through a simple structure:
- Discussion of the item: The item is discussed with the goal of identifying opinions and information on the topic at hand. The general direction of the group and potential proposals for action are often identified during the discussion.
- Formation of a proposal: Based on the discussion a formal decision proposal on the issue is presented to the group.
- Call for consensus: The facilitator of the decision-making body calls for consensus on the proposal. Each member of the group usually must actively state whether they agree or consent, stand aside, or object, often by using a hand gesture or raising a colored card, to avoid the group interpreting silence or inaction as agreement. The number of objections is counted to determine if this step's consent threshold is satisfied. If it is, dissenters are asked to share their concerns with proceeding with the agreement, so that any potential harms can be addressed/minimized. This can happen even if the consent threshold is unanimity, especially if many voters stand aside.
- Identification and addressing of concerns: If consensus is not achieved, each dissenter presents his or her concerns on the proposal, potentially starting another round of discussion to address or clarify the concern.
- Modification of the proposal: The proposal is amended, re-phrased or ridered in an attempt to address the concerns of the decision-makers. The process then returns to the call for consensus and the cycle is repeated until a satisfactory decision passes the consent threshold for the group.
Quaker -based consensus  is said to be effective because it puts in place a simple, time-tested structure that moves a group towards unity. The Quaker model has been employed in a variety of secular settings. The process is intended to allow hearing individual voices while providing a mechanism for dealing with disagreements.   
The following aspects of the Quaker model can be effectively applied in any consensus decision-making process, and is an adaptation prepared by Earlham College:
- Multiple concerns and information are shared until the sense of the group is clear.
- Discussion involves active listening and sharing information.
- Norms limit number of times one asks to speak to ensure that each speaker is fully heard.
- Ideas and solutions belong to the group; no names are recorded.
- Ideally, differences are resolved by discussion. The facilitator ("clerk" or "convenor" in the Quaker model) identifies areas of agreement and names disagreements to push discussion deeper.
- The facilitator articulates the sense of the discussion, asks if there are other concerns, and proposes a " minute " of the decision.
- The group as a whole is responsible for the decision and the decision belongs to the group.
- The facilitator can discern if one who is not uniting with the decision is acting without concern for the group or in selfish interest.
- Ideally, all dissenters' perspectives are synthesized into the final outcome for a whole that is greater than the sum of its parts. 
- Should some dissenter's perspective not harmonize with the others, that dissenter may "stand aside" to allow the group to proceed, or may opt to "block". "Standing aside" implies a certain form of silent consent. Some groups allow "blocking" by even a single individual to halt or postpone the entire process. 
Key components of Quaker-based consensus include a belief in a common humanity and the ability to decide together. The goal is "unity, not unanimity." Ensuring that group members speak only once until others are heard encourages a diversity of thought. The facilitator is understood as serving the group rather than acting as person-in-charge.  In the Quaker model, as with other consensus decision-making processes, by articulating the emerging consensus, members can be clear on the decision, and, as their views have been taken into account, are likely to support it. 
The consensus-oriented decision-making  (CODM) model offers a detailed step-wise description of consensus process. It can be used with any type of decision rule. It outlines the process of how proposals can be collaboratively built with full participation of all stakeholders. This model lets groups be flexible enough to make decisions when they need to, while still following a format based on the primary values of consensus decision-making. The CODM steps include:
- Framing the topic
- Open discussion
- Identifying underlying concerns
- Collaborative proposal building
- Choosing a direction
- Synthesizing a final proposal
Some of the specific contributions of the CODM model include: 1) Starting important topics with open discussion rather than by presenting a pre-formulated proposal, so that a truly collaborative process can ensue. 2) Gathering a list of all needs and concerns expressed by the group to form criteria for all potential proposals to address. 3) taking turns in a unified attempt to build each proposal idea into the best possible proposal before choosing between them. And 4) using empathy in the closure stage to address any unresolved feelings from the process.
Overlaps with deliberative methods
Consensus decision-making models overlap significantly with deliberative methods, which are processes for structuring discussion that may or may not be a lead-in to a decision.
The consensus decision-making process often has several roles designed to make the process run more effectively. Although the name and nature of these roles varies from group to group, the most common are the facilitator, a timekeeper, an empath and a secretary or notes taker. Not all decision-making bodies use all of these roles, although the facilitator position is almost always filled, and some groups use supplementary roles, such as a Devil's advocate or greeter. Some decision-making bodies rotate these roles through the group members in order to build the experience and skills of the participants, and prevent any perceived concentration of power.
The common roles in a consensus meeting are:
- Facilitator: As the name implies, the role of the facilitator is to help make the process of reaching a consensus decision easier. Facilitators accept responsibility for moving through the agenda on time; ensuring the group adheres to the mutually agreed-upon mechanics of the consensus process; and, if necessary, suggesting alternate or additional discussion or decision-making techniques, such as go-arounds, break-out groups or role-playing.   Some consensus groups use two co-facilitators. Shared facilitation is often adopted to diffuse the perceived power of the facilitator and create a system whereby a co-facilitator can pass off facilitation duties if he or she becomes more personally engaged in a debate. 
- Timekeeper: The purpose of the timekeeper is to ensure the decision-making body keeps to the schedule set in the agenda. Effective timekeepers use a variety of techniques to ensure the meeting runs on time including: giving frequent time updates, ample warning of short time, and keeping individual speakers from taking an excessive amount of time.
- Empath or 'Vibe Watch': The empath, or 'vibe watch' as the position is sometimes called, is charged with monitoring the 'emotional climate' of the meeting, taking note of the body language and other non-verbal cues of the participants. Defusing potential emotional conflicts, maintaining a climate free of intimidation and being aware of potentially destructive power dynamics, such as sexism or racism within the decision-making body, are the primary responsibilities of the empath. 
- Note taker: The role of the notes taker or secretary is to document the decisions, discussion and action points of the decision-making body.
Tools and methods
Non-verbal means of expression can also reduce contention or keep issues from spreading out in time across an entire meeting. Various methods of agenda control exist, mostly relying on an explicit chairperson with the power to interrupt off-topic or rambling discourse. This gets more difficult if there is no such chair and accordingly the attitude of the entire group must be assessed by each speaker. Verbal interruptions inevitably become common, possibly in the form of grumbling, muttering, and eventually sharp words, if there is no effective means of cutting off persons making false factual statements or rambling off a topic.
The Levi Hand Signal Technique (LHST) employed by Otesha  "allows meeting participants to register their intent to make two distinct kinds of comments: those that are directly in response to someone else's comment ('reactive comments') and those that are separate thoughts ('unique comments'). Intent to register a reactive comment is signaled by a different hand signal than is intent to register a unique comment. We used an index finger for the former and a full hand for the latter." This clears direct responses to a contentious comment faster—and makes it harder to insert it in a long speakers' list and count on a long delay between the utterance and the challenge to create the appearance of agreement.
"Twinkling fingers", similarly, is a nonverbal way of expressing strong agreement, similar to applause but without the interruption and possibly less intimidation of disagreement than applause or cheers can create. The Occupy movement has used these methods. 
Some consensus decision-making bodies use a system of colored cards to speed up and ease the consensus process. Most often, each member is given a set of three colored cards: red, yellow and green. The cards can be raised during the process to indicate the member's input. Cards can be used during the discussion phase as well as during a call for consensus. The cards have different meanings, depending on the phase in which they are used.  The meaning of the colors are:
- Red: During discussion, a red card is used to indicate a point of process or a breach of the agreed upon procedures. Identifying offtopic discussions, speakers going over allowed time limits or other breaks in the process are uses for the red card. During a call for consensus, the red card indicates the member's opposition (usually a "principled objection") to the proposal at hand. When a member, or members, use a red card, it becomes their responsibility to work with the proposing committee to come up with a solution that works for everyone.
- Yellow: In the discussion phase, the yellow card is used to indicate a member's ability to clarify a point being discussed or answer a question being posed. Yellow is used during a call for consensus to register a stand aside to the proposal or to formally state any reservations.
- Green: A group member can use a green card during discussion to add to the speakers list. During a call for consensus, the green card indicates consent.
Some decision-making bodies use a modified version of the colored card system with additional colors, such as orange to indicate a non-blocking reservation stronger than a stand-aside. 
Hand signals are often used by consensus decision-making bodies as a way for group members to nonverbally indicate their opinions or positions. They have been found useful in facilitating groups of 6 to 250 people. They are particularly useful when the group is multi-lingual.
The nature and meaning of individual gestures varies from group to group. Nonetheless, there is a widely adopted core set of hand signals. These include: wiggling of the fingers on both hands, a gesture sometimes referred to as "twinkling", to indicate agreement; raising a fist or crossing both forearms with hands in fists to indicate a block or strong disagreement; and making a "T" shape with both hands, the "time out" gesture, to call attention to a point of process or order.   One common set of hand signals is called the "Fist-to-Five" or "Fist-of-Five". In this method each member of the group can hold up a fist to indicate blocking consensus, one finger to suggest changes, two fingers to discuss minor issues, three fingers to indicate willingness to let issue pass without further discussion, four fingers to affirm the decision as a good idea, and five fingers to volunteer to take a lead in implementing the decision.  A similar set of hand signals are used by the Occupy Wall Street protesters in their group negotiations. 
Another common set of hand signals used is the "Thumbs" method, where Thumbs Up=agreement; Thumbs Sideways=have concerns but won't block consensus; and Thumbs Down=I don't agree and I won't accept this proposal. This method is also useful for "straw polls" to take a quick reading of the group's overall sentiment for the active proposal.
A slightly more detailed variation on the thumbs proposal can be used to indicate a 5-point range: (1) Thumb-up=strongly agree, (2) Palm-up=mostly agree, (3) Thumb Sideways="on the fence" or divided feelings, (4) Palm down=mostly disagree, and (5) Thumb down=strongly disagree.
Other useful hand signs include:
- Clarifying Question – using your hand to form a "C" shape to indicate that you have a clarifying question, often this hand sign means that a person is invited to ask their question before a vote is taken.
- Point of Information – pointing your index finger upwards to indicate that you have some important factual information that relates to the discussion or decision at hand.
- Process Point – forming a triangle with your hands or hands and arms to indicate that you have an important concern with the meeting or decision-making process.
Dotmocracy sheets provide a way to visibly document levels of agreement among participants on a large variety of ideas. Participants write down ideas on paper forms called Dotmocracy sheets and fill in one dot per sheet to record their opinion of each idea on a scale of "strong agreement", "agreement", "neutral", "disagreement", "strong disagreement" or "confusion". Participants sign each sheet they dot and may add brief comments. The result is a graph-like visual representation of the group's collective opinions on each idea.
Sometimes some common form of voting such as First-past-the-post is used as a fall-back method when consensus cannot be reached within a given time frame. However, if the potential outcome of the fall-back method can be anticipated, then those who support that outcome have incentives to block consensus so that the fall-back method gets applied. Special fall-back methods have been developed that reduce this incentive. Some specific fall-back methods include:
- "Seasoning" the topic by allowing time to pass before continuing the discussion, with the hope that time will bring resolution to unresolved differences.
- Delegating the unresolved topic to a committee that includes representatives of the differing viewpoints so that the differences can be resolved without absorbing too much time in a whole group meeting.
- Using a super-majority decision-rule when an issue is brought back to the whole group after seasoning or discussion in a committee.
- Assigning a committee to rule on whether a "blocking" vote satisfies the criteria for a legitimate block (i.e. Is the block based on a core value? or Is this the type of decision that can be "blocked?")
Criticism of blocking
Critics of consensus blocking often observe that the option, while potentially effective for small groups of motivated or trained individuals with a sufficiently high degree of affinity, has a number of possible shortcomings, notably
- Preservation of the status quo: In decision-making bodies that use formal consensus, the ability of individuals or small minorities to block agreement gives an enormous advantage to anyone who supports the existing state of affairs. This can mean that a specific state of affairs can continue to exist in an organization long after a majority of members would like it to change. The incentive to block can however be removed by using a special kind of voting process.
- Susceptibility to widespread disagreement: Giving the right to block proposals to all group members may result in the group becoming hostage to an inflexible minority or individual. When a popular proposal is blocked the group actually experiences widespread disagreement, the opposite of the consensus process's goal. Furthermore, "opposing such obstructive behavior [can be] construed as an attack on freedom of speech and in turn [harden] resolve on the part of the individual to defend his or her position."  As a result, consensus decision-making has the potential to reward the least accommodating group members while punishing the most accommodating.
- Stagnation and group dysfunction: When groups cannot make the decisions necessary to function (because they cannot resolve blocks), they may lose effectiveness in accomplishing their mission.
- Susceptibility to splitting and excluding members: When high levels of group member frustration result from blocked decisions or inordinately long meetings, members may leave the group, try to get to others to leave, or limit who has entry to the group.
- Channeling decisions away from an inclusive group process: When group members view the status quo as unjustly difficult to change through a whole group process, they may begin to delegate decision-making to smaller committees or to an executive committee. In some cases members begin to act unilaterally because they are frustrated with a stagnated group process.
Consensus seeks to improve solidarity in the long run. Accordingly, it should not be confused with unanimity in the immediate situation, which is often a symptom of groupthink. Studies of effective consensus process usually indicate a shunning of unanimity or "illusion of unanimity"  that does not hold up as a group comes under real-world pressure (when dissent reappears). Cory Doctorow, Ralph Nader and other proponents of deliberative democracy or judicial-like methods view the explicit dissent as a symbol of strength. Lawrence Lessig considers it a major strength of working projects like public wikis. Schutt,  Starhawk  and other practitioners of direct action focus on the hazards of apparent agreement followed by action in which group splits become dangerously obvious.
Unanimous, or apparently unanimous, decisions can have drawbacks.  They may be symptoms of a systemic bias, a rigged process (where an agenda is not published in advance or changed when it becomes clear who is present to consent), fear of speaking one's mind, a lack of creativity (to suggest alternatives) or even a lack of courage (to go further along the same road to a more extreme solution that would not achieve unanimous consent).
Unanimity is achieved when the full group apparently consents to a decision. It has disadvantages insofar as further disagreement, improvements or better ideas then remain hidden, but effectively ends the debate moving it to an implementation phase. Some consider all unanimity a form of groupthink, and some experts propose "coding systems...for detecting the illusion of unanimity symptom."  In Consensus is not Unanimity , consensus practitioner and activist leader Starhawk wrote:
- Many people think of consensus as simply an extended voting method in which every one must cast their votes the same way. Since unanimity of this kind only rarely occurs in groups with more than one member, groups that try to use this kind of process usually end up being either extremely frustrated or coercive. Either decisions are never made (leading to the demise of the group, its conversion into a social group that does not accomplish any tasks), they are made covertly, or some group or individual dominates the rest. Sometimes a majority dominates, sometimes a minority, sometimes an individual who employs "the block". But no matter how it is done, it is NOT consensus. 
Confusion between unanimity and consensus, in other words, usually causes consensus decision-making to fail, and the group then either reverts to majority or supermajority rule or disbands.
Most robust models of consensus exclude uniformly unanimous decisions and require at least documentation of minority concerns. Some state clearly that unanimity is not consensus but rather evidence of intimidation, lack of imagination, lack of courage, failure to include all voices, or deliberate exclusion of the contrary views.
Criticism of majority voting processes
Some proponents of consensus decision-making view procedures that use majority rule as undesirable for several reasons. Majority voting is regarded as competitive, rather than cooperative, framing decision-making in a win/lose dichotomy that ignores the possibility of compromise or other mutually beneficial solutions. Carlos Santiago Nino, on the other hand, has argued that majority rule leads to better deliberation practice than the alternatives, because it requires each member of the group to make arguments that appeal to at least half the participants. A. Lijphart reaches the same conclusion about majority rule, noting that majority rule encourages coalition-building.  Additionally, opponents of majority rule claim that it can lead to a ' tyranny of the majority', a scenario in which a majority places its interests so far above those of an individual or minority group as to constitute active oppression. Some voting theorists, however, argue that majority rule may actually prevent tyranny of the majority, in part because it maximizes the potential for a minority to form a coalition that can overturn an unsatisfactory decision. 
Some advocates of consensus would assert that a majority decision reduces the commitment of each individual decision-maker to the decision. Members of a minority position may feel less commitment to a majority decision, and even majority voters who may have taken their positions along party or bloc lines may have a sense of reduced responsibility for the ultimate decision. The result of this reduced commitment, according to many consensus proponents, is potentially less willingness to defend or act upon the decision.
Outside of Western culture, multiple other cultures have used consensus decision-making. Perhaps the oldest example is the Iroquois Confederacy Grand Council, or Haudenosaunee, which has used consensus in decision-making using a 75% super majority to finalize decisions,  potentially as early as 1142.  In the Xulu and Xhosa (South African) process of indaba, community leaders gather to listen to the public and negotiate figurative thresholds towards an acceptable compromise. The technique was also used during the 2015 United Nations Climate Change Conference.   In Aceh and Nias cultures (Indonesian), family and regional disputes from playground fights to estate inheritance are handled through a musyawarah consensus-building process in which parties mediate to find peace and avoid future hostility and revenge. The resulting agreements are expected to be followed, and range from advice and warnings to compensation and exile.  
Although the modern popularity of consensus decision-making in Western society dates from the women's liberation movement of the 1970s,  and anti-nuclear movement  the origins of formal consensus can be traced significantly further back. 
The most notable of early Western consensus practitioners are the Religious Society of Friends, or Quakers, who adopted the technique as early as the 17th century. Anabaptists, including some Mennonites, have a history of using consensus decision-making  and some believe Anabaptists practiced consensus as early as the Martyrs' Synod of 1527.  Some Christians trace consensus decision-making back to the Bible. The Global Anabaptist Mennonite Encyclopedia references, in particular, Acts 15  as an example of consensus in the New Testament. The lack of legitimate consensus process in the unanimous conviction of Jesus by corrupt priests  in an illegally held Sanhedrin court (which had rules preventing unanimous conviction in a hurried process) strongly influenced the views of pacifist Protestants, including the Anabaptists (Mennonites/Amish), Quakers and Shakers. In particular it influenced their distrust of expert-led courtrooms and to "be clear about process" and convene in a way that assures that "everyone must be heard". 
Japanese companies normally use consensus decision-making, meaning that unanimous support on the board of directors is sought for any decision.  A ringi-sho is a circulation document used to obtain agreement. It must first be signed by the lowest level manager, and then upwards, and may need to be revised and the process started over. 
IETF rough consensus model
In the Internet Engineering Task Force (IETF), decisions are assumed to be taken by rough consensus .  The IETF has studiously refrained from defining a mechanical method for verifying such consensus, apparently in the belief that any such codification leads to attempts to " game the system." Instead, a working group (WG) chair or BoF chair is supposed to articulate the "sense of the group."
One tradition in support of rough consensus is the tradition of humming rather than (countable) hand-raising; this allows a group to quickly tell the difference between "one or two objectors" or a "sharply divided community", without making it easy to slip into " majority rule ". 
Much of the business of the IETF is carried out on mailing lists, where all parties can speak their view at all times.
Social constructivism model
In 2001, Robert Rocco Cottone published a consensus-based model of professional decision-making for counselors and psychologists. Based on social constructivist philosophy, the model operates as a consensus-building model, as the clinician addresses ethical conflicts through a process of negotiating to consensus. Conflicts are resolved by consensually agreed on arbitrators who are defined early in the negotiation process.
US Bureau of Land Management collaborative stakeholder engagement
The United States Bureau of Land Management's policy is to seek to use collaborative stakeholder engagement as standard operating practice for natural resources projects, plans, and decision-making except under unusual conditions such as when constrained by law, regulation, or other mandates or when conventional processes are important for establishing new, or reaffirming existing, precedent.
Modern large-group Quaker processes
FUM/FGC Friends conduct business in yearly meetings of perhaps 100 to 500 participants. Over the last three centuries they have evolved a number of practices peculiar to their aims. The following practices are traditional in both New York Yearly Meeting and in New England Yearly Meeting:
- A typical yearly meeting session has a presiding clerk, one or two recording clerks and a reading clerk on stage. Partitioning the work load with extra clerks lowers the stress level on the presiding clerk.
- Business sessions start with a period of corporate silent worship.
- A period of silent worship, perhaps thirty seconds, is allotted by the presiding clerk after each person speaks. This slows the pace of the business meeting down and allows people to contemplate people's messages.
- The use of wireless microphones helps to slow down the pace of the meeting. Volunteer microphone runners are instructed to walk at a reasonably slow pace toward someone standing and waiting to be recognized.
- The clerk often recognizes who speaks first, then second, then third.
- A pastoral care team upholds the presiding clerk, or simply the clerk, in prayer.
- Attempts are made to take minor editing functions off of the floor of the meeting. Minutes are polished by a committee before presenting them on the meeting floor. All suggested small corrections are incorporated either on the spot by the caucusing clerks, or at a special impromptu meeting after the current business session ends. Corrected minutes are then brought back onto the floor of the meeting at a later date.
- Major, complex concerns result in a called threshing session, a meeting of people most concerned about the issue.
- New England Yearly Meeting has discovered the benefits of anchor groups, groups of about ten participants who meet every day during a multi-day yearly meeting. People sometimes need to vocalize their personal opinions on issues to a few other people, in part because people think aloud.
Every 20 or 30 years, each yearly meeting's consensus practices are re-codified in a new edition of that yearly meeting's Faith and Practice book.
Additional criticism from biblical and philosophical perspectives
As a notable example of the failure of unanimity in the Western canon, New Testament historian Elaine Pagels cites the Sanhedrin's unanimous vote to convict Jesus of Nazareth.  To a Jewish audience familiar with that court's requirement to set free any person unanimously convicted as not having a proper defense, Pagels proposes that the story is intended to signal the injustice of unanimous rush to agreement and Jesus' lack of a defender.  She cites the shift away from this view and towards preference for visible unanimity as a factor in later "demonization" of Jews, pagans, heretics (notably Gnostics) and others who disagreed with orthodox views in later Christianity. Unanimity, in other words, became a priority where it had been an anathema.
High-stakes decision-making, such as judicial decisions of appeals courts, always require some such explicit documentation. Consent however is still observed that defies factional explanations. Nearly 40% of Supreme Court of US decisions, for example, are unanimous, though often for widely varying reasons. "Consensus in Supreme Court voting, particularly the extreme consensus of unanimity, has often puzzled Court observers who adhere to ideological accounts of judicial decision making." Historical evidence is mixed on whether particular Justices' views were suppressed in favour of public unity. 
Another method to achieve more agreement to satisfy a strict threshold a voting process under which all members of the group have a strategic incentive to agree rather than block. However, this makes it very difficult to tell the difference between those who support the decision and those who merely tactically tolerate it for the incentive. Once they receive that incentive, they may undermine or refuse to implement the agreement in various and non-obvious ways. In general voting systems avoid allowing offering incentives (or "bribes") to change a heartfelt vote.
- Abilene paradox: Consensus decision-making is susceptible to all forms of groupthink, the most dramatic being the Abilene paradox. In the Abilene paradox, a group can unanimously agree on a course of action that no individual member of the group desires because no one individual is willing to go against the perceived will of the decision-making body. 
- Time Consuming: Since consensus decision-making focuses on discussion and seeks the input of all participants, it can be a time-consuming process. This is a potential liability in situations where decisions must be made speedily, or where it is not possible to canvass opinions of all delegates in a reasonable time. Additionally, the time commitment required to engage in the consensus decision-making process can sometimes act as a barrier to participation for individuals unable or unwilling to make the commitment.  However, once a decision has been reached it can be acted on more quickly than a decision handed down. American businessmen complained that in negotiations with a Japanese company, they had to discuss the idea with everyone even the janitor, yet once a decision was made the Americans found the Japanese were able to act much quicker because everyone was on board, while the Americans had to struggle with internal opposition.
- Consensus based assessment
- Consensus democracy
- Consensus government
- Consensus reality
- Consensus theory of truth
- Copenhagen Consensus
- Libertarian socialism
- Liberum veto
- Major consensus narrative
- Polder Model
- Seattle process
- Social representations
- Truth by consensus
- . Merriam-Webster Dictionary . Retrieved 2011-08-29 .
- . Consensusdecisionmaking.org . Retrieved 2011-08-29 .
- Hartnett, T. (2011). Consensus-Oriented Decision Making. Gabriola Island, BC, Canada:New Society Publishers.
- Rob Sandelin. . Northwest Intentional Communities Association guide to consensus . Northwest Intentional Communities Association. Archived from on February 9, 2007 . Retrieved 2007-01-17 .
- . Groupfacilitation.net . Retrieved 2011-08-29 .
- Tree Bressen (2006),
- Kaner, S. (2011). Facilitator's Guide to Participatory Decision-making. San Francisco, CA:Jossey-Bass.
- Norberg v. Wynrib,  2 S.C.R. 226 (Supreme Court of Canada)
- Christian, D. Creating a Life Together: Practical Tools to Grow Ecovillages and Intentional Communities. (2003). Gabriola Island, BC, Canada:New Society Publishers.
- Richard Bruneau (2003). . Participatory Decision-Making in a Cross-Cultural Context . Canada World Youth. p. 37. Archived from (DOC) on 2007-09-27 . Retrieved 2007-01-17 .
- Consensus Development Project (1998). . Frontier Education Center. Archived from on December 12, 2006 . Retrieved 2007-01-17 .
- Rachel Williams; Andrew McLeod (2008). (PDF) . Cooperative Starter Series . Northwest Cooperative Development Center. Archived from (PDF) on March 14, 2012 . Retrieved 2012-12-09 .
- Dorcas; Ellyntari (2004). . Retrieved 2007-01-17 .
- . Canadian Cohousing Network. Archived from on February 26, 2007 . Retrieved 2007-01-28 .
- Jeppesen, Sandra; Adamiak, Joanna (2017). "Street Theory: Grassroots Activist Interventions in Regimes of Knowledge". In Haworth, Robert H.; Elmore, John M. . PM Press. p. 291. ISBN 978-1-62963-319-0.
- . Consensus Decision Making . ConsensusDecisionMaking.org. 2015-02-17 . Retrieved 2015-02-17 .
- . The Common Place. 2005. Archived from on October 15, 2006 . Retrieved 2007-01-17 .
- . Consensus Decision Making . Seeds for Change. 2005-12-01 . Retrieved 2007-01-17 .
- Quaker Foundations of Leadership (1999). Richmond, Indiana: Earlham College. Retrieved on 2009-03-01.
- Woodrow, P. (1999). 2008-08-28 at the Wayback Machine. Kellogg-Earlham Program in Quaker Foundations of Leadership. Retrieved on 2009-03-01.
- Berry, F. and M. Snyder (1999). 2008-10-11 at the Wayback Machine. National Conference on Teaching Public Administration, Colorado Springs, Colorado, March 1998. Retrieved on 2009-03-01.
- By Tree Group, Quaker group facilitators. Downloaded 26 Oct. 2014
- Quaker Foundations of Leadership (1999). . Richmond, Indiana: Earlham College. Retrieved on 2009-03-01.
- Maine.gov. 2008-12-12 at the Wayback Machine. State of Maine Best Practices. Retrieved on: 2009-03-01.
- "Consensus-Oriented Decision-Making: The CODM Model for Facilitating Groups to Widespread Agreement"
- C.T. Lawrence Butler; Amy Rothstein. . Food Not Bombs Publishing. Archived from on October 26, 2011 . Retrieved 2011-10-31 .
- Sheila Kerrigan (2004). . Community Arts Network. Archived from on June 19, 2006 . Retrieved 2007-01-17 .
- Lori Waller. . The Otesha Project. Archived from on 2017-03-12 . Retrieved 2007-01-17 .
- Berit Lakey (1975). . Network Service Collaboration . Retrieved 2007-01-17 .
- . Mosaic Commons . Retrieved 2007-01-17 .
- [Jan Havercamp, "Non-verbal communication – a solution for complex group settings", Zhaba facilitators collective, 1999.]
- (PDF) . Zhaba Facilitators Collective. Archived from (PDF) on July 14, 2006 . Retrieved 2007-01-18 .
- (PDF) . Seeds for Change. Archived from (PDF) on September 27, 2007 . Retrieved 2007-01-18 .
- . Freechild.org . Retrieved 2008-02-04 .
- The Salt Lake Tribune. .
- Dotmocracy facilitator's resource website
- Saint S, Lawson JR (1994) Rules for reaching consensus: a modern approach to decision making. Pfeiffer, San Diego
- Heitzig J, Simmons FW (2010). Soc Choice Welf 35.
- The Common Wheel Collective (2002). . The Collective Book on Collective Process . Archived from on 2006-06-30 . Retrieved 2007-01-17 .
- Alan McCluskey (1999). . Retrieved 2007-01-17 .
- Welch Cline, Rebecca J (1990). . Communication Quarterly . 38 (2): 112–126. doi:.
- Joseph Michael Reagle, Jr.; Lawrence Lessig (30 September 2010). . MIT Press. p. 100. ISBN 978-0-262-01447-2 . Retrieved 10 June 2011 .
- Schutt, R. (August 31, 2010). . The Vernal Education Project. Papers on Nonviolent Action and Cooperative Decision-Making.
- Starhawk - a practitioner's interpretation of Schutt. February 13, 2008, at the Wayback Machine.
- Schermers, Henry G.; Blokker, Niels M. (2011). . p. 547. ISBN 9004187987 . Retrieved 2016-02-29 .
- Cline, Rebecca J. Welch (2009). . Communication Quarterly . 38 (2): 112–126. doi:.
- February 21, 2014, at the Wayback Machine., Starhawk.
- Friedrich Degenhardt (2006). . World Council of Churches. Archived from on 2006-12-06 . Retrieved 2007-01-17 .
- McGann, Anthony J. The Logic of Democracy: Reconciling, Equality, Deliberation, and Minority Protection. Ann Arbor: University of Michigan Press. 2006. ISBN 0-472-06949-7.
- Anthony J. McGann (2002). (PDF) . Center for the Study of Democracy . Retrieved 2008-06-09 .
- M. Paul Keesler (2008). . Mohawk – Discovering the Valley of the Crystals . North Country Press. ISBN 9781595310217 . Retrieved 2016-02-29 .
- Bruce E. Johansen (1995). . Akwesasne Notes . Retrieved 2007-01-17 .
- . 10 December 2016 – via Reuters.
- Rathi, Akshat. .
- p. 151
- Anthony, Mely Caballero (1 January 2005). . Institute of Southeast Asian Studies – via Google Books.
- David Graeber; Andrej Grubacic (2004). . ZNet. Archived from on February 17, 2007 . Retrieved 2007-01-17 .
- Sanderson Beck (2003). . Sanderson Beck . Retrieved 2007-01-17 .
- Ethan Mitchell (2006). . Philica . Retrieved 2007-01-17 .
- Abe J. Dueck (1990). . Direction . Retrieved 2007-01-17 .
- Ralph A Lebold (1989). . Global Anabaptist Mennonite Encyclopedia Online . Global Anabaptist Mennonite Encyclopedia Online. Archived from on March 13, 2007 . Retrieved 2007-01-17 .
- Elaine Pagels (1996). . Random House. ISBN 0-679-73118-0 . Retrieved 23 April 2012 .
- "Consensus ad idem: a protocol for development of consensus statements." Can J Surg 2013; 56 (6); 365
- Vogel, Ezra F. (1975). . p. 121. ISBN 0520054687.
- . Japanese123.com. Archived from on August 11, 2011 . Retrieved 2011-08-29 .
- RFC. "IETF Working Group Guidelines and Procedures."
- . The Internet Society. 2006 . Retrieved 2007-01-17 .
- Cottone, R. R. (2001). The social constructivism model of ethical decision making. "Journal of Counseling and Development," vol. 79, pp. 39-45.
- (PDF) . Bureau of Land Management. 2009. Archived from (PDF) on January 14, 2012.
- . Archived from on May 11, 2013.
- . Journal of Empirical Legal Studies . 9 (1): 129–148. doi:.
- Harvey, Jerry B. (Summer 1974). "The Abilene Paradox and other Meditations on Management". Organizational Dynamics . 3 (1): 63–80. doi:.
- . Strategic Leadership and Decision Making . National Defense University . Retrieved 2007-01-17 .
- Tomalin, Barry; Knicks, Mike (2008). "Consensus or individually driven decision-". The World's Business Cultures and How to Unlock Them . Thorogood Publishing,. p. 109. ISBN 978-1-85418-369-9.