There are a lot of meaningless phrases that make the rounds. One of these that wannabe intelligent people pass around to make themselves seem rational is “evidence-based decision making.” This phrase is often used in politics and public policy, where one side will use it to describe the adoption of policies they like (with the implication that the other side is not using evidence-based decision making). It is also contrasted with ideological decision-making.
Now, I am not against using evidence to inform a decision; using evidence is a good thing. As a stand-alone, face-value concept it is unobjectionable, how can anybody be against evidence? But this unobjectableness is the reason for its meaninglessness.
Everybody in politics and public policy uses ‘evidence’ to make decisions. In the days of yore, the autocratic king may occasionally have indulged himself in the occasional bout of thoughtless whimsy, but in today’s bureaucratic world, no policy decision is made without rounds upon rounds of evidence, discussion, writing, revision, etc. Even the autocratic king’s bouts of whimsy were usually based on evidence and fact. “People over six feet are tall” and “an army of tall people amuses me” are both evidence-based facts that can be used to inform policy. The other may not be interpreting evidence the same way as you, they may impute differing levels of legitimacy to certain forms or instances of evidence than you, and they may be using the evidence to pursue different values than you, but they are using evidence.
Using the phrase evidence-based decision making in a modern public policy context is as meaningless as going around saying a four-sided square when discussing geometry. But meaningless phrases are commonplace, the context of the phrase reveals a more important and deep stupidity.
Any time someone uses the phrase with any intent at creating even the tiniest amount of semantic meaning, the semantic meaning is (either implicitly or explicitly) evidence-based as compared to ideological (or opinion-based, which is the same thing), where the ideological is irrational (and therefore wrong). Nobody ever points out the idiocy of this semantic meaning.
To make a trite example, the fact that you need to breathe oxygen or you die has absolutely no decision-making implications standing on its own. Only when you create a value system around breathing does the need to breathe factor into decision-making. The suicide and the astronaut will both make entirely different evidence-based decisions on that particular fact.
To make a decisions requires a value-system: the value system under which the decision is being made is the most important part of any decision-making. The value system will create a goal. Reason will create a plan to achieve a goal. Evidence upon which to reason is the final and least important part of a decision-making architecture.
Another word for value-system is ideology. All public-policy decisions are first and foremost ideological. Anybody who thinks they aren’t is so ideologically brainwashed that they are not even aware that they have their own ideology.
To call attention to the fact you use or favour evidence-based decision making reveals either:
1) a very weak decision-making architecture if using evidence is the best you can say about it,
2) the shallowness of your own thinking, if the facts you use are the deepest you can delve in your own decision-making architecture,
3) ideological blindness, if you can not even see that you are making decisions under a value system,
or, it might reveal something more sinister:
4) the purposeful distortion of language to fool the gullible into accepting a particular ideological as reality.
Practically speaking, the use of the phrase ‘evidence-based decision making’ as related to public policy is usually a signal you can safely ignore the surrounding verbiage as wasteful rhetoric, empty-headed stupidity, and/or attempted manipulation. Rarely will it be used in any commentary on public policy that is worth listening to.
Note: Evidence-based decision-making started out as a concept for medical research and practice. In the medical context, it is a reasonable approach and something reasonable to talk about, as the ideology of medicine is mostly firmly established and medical “conflict” (barring corruption) is based around finding the best methods of healing to input into this system.