Ecology: one value, several ways of turning it into rules

The standard forbids or imposes: it is clear, immediately checkable, and does not adapt to particular situations. The price signal makes what one wants to reduce more expensive: it lets each person choose how to adapt, and weighs more heavily on constrained budgets if nothing compensates for it.

Public investment funds the infrastructure that makes the desired behaviour accessible: it avoids individual constraint, is expensive and takes time. Capped quantity, with tradable quotas, sets a total result and lets the market distribute the effort: it guarantees the volume and makes the price uncertain.

None of these instruments is intrinsically superior. Their effectiveness depends on the behaviour targeted, on the existence of accessible alternatives, and on the capacity to monitor. The same objective may therefore justify different instruments according to sector.

The first bears on the scale of the effort asked of individuals compared with that asked of organisations and states. Two people equally convinced of the objective may differ entirely on the distribution, without either being less sincere than the other.

The second bears on the role expected of technology. Some consider that most of the effort will pass through technical solutions and therefore through investment, others that it will pass through a reduction of uses and therefore through the standard or the price. This disagreement is partly a disagreement of forecast, and therefore settleable by facts, but only in the long term.

An instrument that is effective but rejected produces no effect, since it is abandoned or circumvented. That is why the question of acceptability is not a political supplement to technical analysis: it is part of it.

Work on pricing measures observes that their acceptance depends strongly on the announced use of the revenues and on the existence of available alternatives. The same measure may therefore be accepted or rejected according to what accompanies it, independently of its content.

This field has one particularity: the cost is immediate and the benefit deferred, sometimes by a generation. This shifts the debate towards a question of time preference, which is not technical and which data do not settle.

It is also what makes long-term commitments fragile: they bind a decision-maker who will no longer be in office when the result arrives. Hence the importance of monitoring and revision mechanisms, which are often the most debated part of a text.

Asking someone whether they care about the environment produces an almost unanimous and uninformative answer. Positions part company on questions of the kind: do you prefer a clear prohibition or a price that leaves the choice, and who should bear the cost of the transition?

Put that way, the ecological dimension ceases to be a test of adherence to a cause and becomes what it is: a set of preferences about instruments of public action, comparable to those bearing on health or education.