Trilemma

With all these dilemmas and trilemmas crowding the mind, if one did not know better, one might be tempted to doubt whether any such versions were ever made at all.

At the most general level, policymakers in open economies face a macroeconomic trilemma: 1. to stabilize the exchange rate; 2. to enjoy free international capital mobility; 3. to engage in a monetary policy oriented toward domestic goals. Because only two out of the three objectives can be mutually consistent, policymakers must decide which one to give up.

The UK government has forced itself into a trilemma in which it has adopted three positions, only two of which can be achieved at any one time: to avoid a hard border within the island of Ireland; for the UK as whole to leave both the customs union and the single market; and to rule out any special arrangements for Northern Ireland in relation to a customs union and single market.

The trilemma states that it is impossible for national governments to have all three of the following institutions in place at the same time: an autonomous monetary policy, a fixed foreign exchange rate, and full capital mobility. […] The present context of economic and political fragmentation, however, suggests that the best, if not only, way to deal with fragmentation under the two trilemmata – the Mundellian and the one described by Rodrik – is anything but national self-sufficiency.

In computing, the unconquerable trilemma is embodied in the well-known CAP theorem for distributed systems, also called Brewer’s CAP theorem. This states that any distributed database can only attain two of three guarantees: consistency, availability and partition tolerance.

It has been remarked as a characteristic of the late Sir Robert Peel, that in introducing his measures to the House of Commons, he often used the trilemma. "Three courses are before us—to go backward, to stand still, to go forward. We cannot go backward; we cannot stand still; we must, then, go forward."

And in anticipation of it, while he [Johann Joseph Ignaz von Döllinger] declares at one moment that it would be profane to limit Divine Providence to an alternative, he affirms in the next that there can be no harm whatever in shutting it up to a supposed exhaustive trilemma.

In three instances, the format of a trilemma, consisting of three obviously contradictory statements, were chosen to induce a more in-depth deliberation and careful consideration of the item response. […] A questionnaire was submitted to further analysis if certain requirements were fulfilled: (1) the multiple choice item regarding mind–body, the three trilemmata, and the multiple choice item regarding belief in God were answered, and (2) fewer than four missing data from the core of 49 remaining items.