The concept of presupposition can be approached as a logical or as a linguistic issue.

1. A logical issue

The problem of presupposition was first addressed within the field of logic. The logic of the analyzed proposition postulates that propositions such as “all As are Bs” have two truth-values, the true and the false. The problem arises when the reference of A and B is void (there are neither A nor B), as in “unicorns can fly (are flying beings)” or “no unicorn is a dragon”. In this case, is the proposition “all As are Bs” true or false? Let us consider the declaration “the king of France is bald”, as said in 1905. It is impossible to attribute a truth-value to this statement, since in 1905, and still today, the French Republic has no king (Russell 1905).

From the point of view of logical technique, it is sufficient to add the premises “there are As”, and “there are Bs”, or “there is one, and just one King of France”. An apparently mono-propositional statement such as “the king of France is bald” is then translated into logical language via the conjunction of three propositions, each having its own truth-value:

 “there is a King of France” & “there is only one King of France” & “he is bald”.

In 1905 or 2017, the first of the three propositions is false. It follows that the conjunction of logical propositions representing the statement “the king of France is bald” is simply false. This analysis was criticized for failing to reflect the linguistic intuition of the ordinary speaker, for whom the statements “there is a King of France” and “this King is bald” do not have the same status in the original sentence. This is true, but the objection is irrelevant, since formal logic does not aim to represent linguistic intuition, but wants to solve a technical problem, and this is what it does.

2. A linguistic issue

Ordinary statements can synthetize different judgments, having different semantic and discursive statuses.

2.1 The multi-layered structure of meaning

The presupposition is defined as an element of the semantic content of the utterance that resists negation and interrogation. The statement “Peter no longer smokes” presupposes that “Peter used to smoked”, and poses that “now, Peter does not smoke”. The negative statement “Peter has not stopped smoking” and the interrogative “has Peter stopped smoking?” share this presupposed content “Peter used to smoke”. Negation and interrogation deal with the posed content (“Peter smokes now”), and do not concern the presupposed content.

This multi-layered structure of sentences is one of the major features which differentiate statements made in ordinary language from logical propositions.

2.2 Presupposition as a speech act and the “many questions” issue

Ducrot redefines presupposition as a strategic action (an illocutionary act) made with the aim of influencing, that is to say, restricting the speech possibilities of the conversational partner. The act of presupposition is a discursive power grab by which the speaker performs “an act of legal value, and therefore an illocutionary act […] [this act] transforms the speech possibilities of the interlocutor, […] modifies the listener’s right to speak” (1972, p. 91).

Consider the following question:

Interviewer — What are you going to do to fight corruption within your own party?

The question presupposes that “there are corrupt people and practices within your party”. The interviewee is given a choice:

(i) Either he or she accepts the presupposed claim and gives an answer within the range of pre-formatted, expected answers such as:

Interviewee — I’ll exclude (suspend) all suspects (the members under investigation).

This answer respects the linguistic orientation of the question. It falls perfectly within the frame of dialogue as established by the first turn. The interviewee submits to the interviewer.

(ii) He or she might also reject the presupposed claim:

Interviewee — To my knowledge, there is no (proved) case of corruption within my party

This second answer reframes the routine consensual dialogue; the interviewee rejects the claim made by the interviewer, and the dialogue takes on a character, becoming uncompromising and polemical, opening an argumentative2 situation structured by the issue “are there (proved) cases of corruption in the party?” The rejection of the presupposed assumption “[is] always regarded as aggressive: it personalizes the debate, which turns into a quarrel. […] To attack the opponent’s assumptions is to attack the adversary himself” (Ducrot 1972, p. 92). The presupposition seeks to impose an “ideological framework” (id., p. 97) on the later dialogue, that is, to direct the partner’s speech. S. Many Questions; Conditions of Discussion; Persuasion.

It goes without saying that presupposition phenomena are not limited to dialogue, but, as always, dialogue serves to clarify any issues. A monologue that would not respect its own presuppositions would be inconsistent, while, in a dialogue, the rejection of a presupposition is contentious. In reality, dialogue (i) develops under the same conditions as a monologue.