• • Lat. onus probandi; Lat. onus “charge, burden”; probandi, from probare “to make believable, to make accept, to prove”.

The burden of proof plays a fundamental role in argument. It is a conservative principle, like the principle of inertia in physics: “I keep doing business as usual unless I have a good reason to change”. Mill reports an anecdote that vividly illustrates the heaviness of the burden of proof imposed by a conservative society upon social innovators, S. Calm.

The propounder of a new truth, according to this doctrine should stand, as stood, in the legislation of the Locrians, the proposer of a new law, with a halter round his neck, to be instantly tightened if the public assembly did not, on hearing his reasons, then and there adopt his proposition. People who defend this mode of treating benefactors, cannot be supposed to set much value on the benefit; and I believe this view of the subject is mostly confined to the sort of persons who think that new truths may have been desirable once, but that we have had enough of them now.([1859]. p. 88)

In court, the burden of proof is expressed by the presumption of innocence “a person is presumed innocent until proved guilty”; that is, the accusation must provide positive evidence of the accused’s guilt. The stabilization of the burden of proof is an institutional decision, organizing the situation; the last word is left to the defendant.

In informal social debates, there is no clear preliminary agreement about who supports the burden of proof, and the proponent can try to shift it onto the adversary. ​​It becomes a stake of the debate.

The doxa can be defined according to the same principle: an endoxon, that is a fragment of the doxa, is best defined not as a “probable” belief, but as a belief which is not subject to the burden of proof, and is, accordingly, considered to be “normal” by the given group. The individual challenging an accepted proposition bear the burden of proof, and has to provide good reasons. This is why Descartes, willing to reject all his pre-established beliefs, must back this radical doubt by the hypothesis of the Evil Genius (Descartes [1641], First Meditation). S. Rules.

When it comes to current trends and fashions, the burden of proof is reversed: “it is new, it has just come out!” is a direct argument for buying the product in question. Good reasons are instead needed for not following fashion, not adopting new theories, and not voting for a new candidate.

Burden of proof and Initiative

Hamblin has redefined the burden of proof in a language game as attributed to the player taking the initiative, that is, making the first move. This definition can be transposed to highly argumentative multi-speaker interactions, where the first turn is generally allocated to the person supporting the proposal to be discussed. In a debate on the legalization of drugs, the facilitator addresses the first question to a supporter, not to an opponent of legalization.

The burden of proof relates to a question and a proposal. If the opponent makes a counter-proposal, he will bear the corresponding burden of proof.

The burden of proof may vary with the group involved, and where the debate takes place. If the doxa of the group is that no prohibition should apply to drug consumption, then, in this group, the supporter of the prohibition will have to justify his stance.