In ethics we use the term “pro tanto”, meaning “to that extent”, to refer to things that have some bearing on what we ought to do but that can be outweighed. The fact that your dog is afraid of the vet is a pro tanto reason not to take him. But perhaps you ought to take him despite this pro tanto reason not to, because keeping him in good health is worth the cost of a single unpleasant experience. If that’s true then we say you have “all things considered” reasons to take your dog to the vet.
In AI ethics, we often point to things that systems do that are harmful. A system might make biased decisions, use a lot of energy in training, produce toxic outputs, and so on. These are all pro tanto harms. Noting that a system does these things doesn’t tell us about the overall benefits or harms of the system or what we have all things considered reasons to do. It just tells us about one particular harm the system causes.
It’s useful to identify pro tanto harms. Pro tanto harms give us pro tanto reasons to do things. When we identify a pro tanto harm we have a pro tanto reason to fix the problem, to analyze it more, to delay deploying the system, to train systems differently in the future, and so on.
But most things that have any significance in the world create some pro tanto harms. And identifying pro tanto harms often doesn’t give us all that much information about what we should do all things considered, including whether we should do anything to reduce the pro tanto harm.
To see why, suppose an article points out that some surgical procedure results in painful stitches. The article draws no conclusions from this: it merely points out one bad thing about the surgery is that it results in these painful stitches, and describes the harm these stitches do in some detail.
There are three ways the harm of these stitches could be mitigated: by not performing the surgery, by giving patients stronger painkillers, or by reducing the length of the incision. But the surgery is essential for long-term health, the stronger painkillers are addictive, and a smaller incision is associated with worse outcomes. In fact, patients with larger incisions who are given fewer painkillers do much better than those from any other group.
In this case, although the pain of the surgery is a pro tanto harm, we actually have all things considered reasons to take actions that will increase that harm, since we ought to increase incision length and give fewer painkillers.
So it’s a mistake to assume that if we identify a pro tanto harm from an AI system, it must be the case that someone has done something wrong, something needs to be done to correct it, or the system shouldn’t be deployed. Maybe none of those things are true. Maybe all of them are. We can’t tell based solely on a discussion of the pro tanto harm alone.
While pro tanto harms don’t entail that we have all-things-considered reasons to do things differently, they do waggle their eyebrows suggestively while mouthing ‘look over there’.
