Inacceptable vs. Unacceptable

Unacceptable

Acceptability is the characteristic of a thing being subject to acceptance for some purpose. A thing is acceptable if it is sufficient to serve the purpose for which it is provided, even if it is far less usable for this purpose than the ideal example. A thing is unacceptable (or has the characteristic of unacceptability) if it deviates so far from the ideal that it is no longer sufficient to serve the desired purpose, or if it goes against that purpose. From a logical perspective, a thing can be said to be acceptable if it has no characteristics that make it unacceptable:

We say that a theory Δ is acceptable if for any wff α, Δ does not prove both α and ¬α.

Hungarian mathematician Imre Lakatos developed a concept of acceptability “taken as a measure of the approximation to the truth”. This concept was criticized in its applicability to philosophy as requiring that better theories first be eliminated. Acceptability is also a key premise of negotiation, wherein opposing sides each begin from a point of seeking their ideal solution, and compromise until they reach a solution that both sides find acceptable:

When a proposal or counter-proposal is received by an agent, it has to decide whether it is acceptable. If it is, the agent can agree to it; if not, and alternative that is acceptable to the receiving agent needs to be generated. Acceptability is determined by searching the hierarchy. If the proposal is a specification of at least one acceptable goal, the proposal is acceptable. If it is the specification of at least one unacceptable goal, the proposal is clearly unacceptable.

Where an unacceptable proposal has been made, “a counterproposal is generated if there are any acceptable ones that have had already been explored”. Since the acceptability of proposition to a participant in a negotiation is only known to that participant, the participant may act as though a proposal that is actually acceptable to them is not, in order to obtain a more favorable proposal.