CONSENSUS

1. Consensus as agreement

See Agreement; Persuasion

2 Argument from consensus

The label argument from consensus, appeal to consensus, covers a family of arguments claiming that a belief is true or that things must be done in such and such a way on the basis that everyone thinks or does so, and that other proposals should be rejected.

We have always thought, wished, done … so; so, buy (please, do…) so.
Everybody loves so-and-so product.
Everybody puts so-and-so ketchup on their burgers!

It implies that by disregarding the existing consensus, the proponent of a new action or a new idea, that is the opponent of the consensus, risks being excluded from that community, see burden of proof.

The universal consensus argument claims that “all people in all times have thought this way things have always been done this way”.
The existence of God has been argued on the basis of the universal consensus argument.

The argument from the relative (partial) consensus includes the argument from majority, the argument from number (Latin ad numerum; numerus, “number”) and related expressions:

The majority / many people … think, wish, do … X.
Three million Syldavians have already adopted it!
My book is selling better than yours.
He is a famous actor.

Common Sense — The argument of consensus is the kind of authority generously granted to traditional wisdom or to common sense, S. Authority.

I know that all true Syldavians agree with this decision
Only the extremes attack me, all people of common sense will agree with me.

The populist argument is based on a real or supposed consensus among (or attributed to) the people, see Ad Populum.

Bandwagon argument and fallacy — The bandwagon argument is a special case of the consensus argument. The bandwagon is the decorated chariot that leads the orchestra through town, the bandwagon argument adds joy and enthusiasm to the dry consensus argument. To get on the bandwagon is to follow the popular movement, to participate in a popular “emotion” in the etymological sense of “a public upheaval”. Joining a party to have fun and sing along should not be condemned as systematically fallacious; but, from the perspective of any opposing party, climbing on the bandwagon can be seen as fallacious, as a follow-the-group or follow-my-leader attitude, sheepish behavior, as uncritically adopting the views of the most vocal or visible group.