Rock climbing is a good metaphor for clinical reasoning and decision-making.
If you go climbing, you can plan a route from the bottom to the top in advance, but when you are actually in the process of ascending the rock face, you have to deal with the actual material physical reality you find in front of you. If that turns out to be different from your previous plan, then the plan gets adjusted to accommodate what you are really dealing with in the moment. If you try to privilege the theoretical plan over the actual facts, things can end very badly very fast.
To get from one place on the rock to the next place without falling, you make sure that you are in a stable position where you currently are, and you look for a way to get safely to the next place you want to be. You repeat this process over and over, and at the end--if all goes well--all those decisions in the moment about how to get from one place to the next lead you to reach the summit you were aiming for all along.
The reason that this is metaphorically like clinical decision-making and reasoning is that need to ensure that you are first in a stable place before you extend yourself to get to the next place.
Like climbing, reasoning is a process--the culmination of many smaller decisions along the way. If you take too many unwarranted risks along the way, you can lose control of the process.
Unlike in individual climbing, however, the one most harmed by a bad outcome in clinical decision-making is someone else: the client.
That's why we have an extra responsibility to do the best job in getting it right that we possibly can--our clients trust us as the experts.
Source: http://upload.wikimedia.org/wikipedia/commons/6/66/Free_solo.jpg accessed 9 August 2012
As we've seen in the previous post, deductive reasoning helps you to get from one point to the next--from the general to the specific--in a safe and valid way, but the kinds of questions it can support are rather limited in comparison to the situations we often encounter in clinical situations. It's a safe and easy line from one point to the next, and the valid results may be exactly what you need in particular situations.
Inductive reasoning is somewhat more powerful, as it can take you from the specific to making generalizations about how things work in the material physical universe--but, by the nature of taking on that task, it's possible to do every thing right--to begin with a valid starting point, to reason in a flawlessly valid way--and to still end up with invalid conclusions, such as "All swans are white". It's riskier than deduction, but--if it succeeds--it opens the door to more possibilities than deductive reasoning alone can provide.
Among other things, it's this recognition that you can do everything right and still end up with invalid conclusions that makes all of scientific knowledge provisional (it holds unless and until it is replaced with better evidence) and contingent (hanging together as part of an integrated whole with other knowledge).
The old joke about how scientists never say anything without including error bars (to show their level of confidence that the statement is correct) references this aspect of scientific knowledge.
Source: http://upload.wikimedia.org/wikipedia/commons/d/df/Confidenceinterval.png accessed 9 August 2012
You will, of course, hear statements made with absolute certainty, but that certainty comes from some place other than science.
The fact that scientific knowledge is contingent and provisional does not, however, mean that it is totally random--that anything goes, and therefore, you can just make up anything you want and it will be every bit as valid as anything scientists have spent centuries testing.
The idea that nothing has any meaning at all, so it doesn't really matter what you claim, is a kind of nihilism, and we're not going to indulge in nihilism here.
Scientific knowlege always has a confidence level of how much we are sure it is true attached to it. That confidence level is never 100%--we are never totally certain without any doubt at all--but in many cases, it does get pretty close. We have tested that knowledge, and reliably repeated it so much that, for all practical purposes, we can proceed to build on it as though it were actually 100% certain.
We can trust it as a safe enough platform in our climb to use it as a base for the next bit of knowledge, reasoning, or clinical decision-making.
This is why the more extravagant claims of energy healers don't hold up--they contradict what we have spent centuries rigorously testing about how energy actually does work in the material physical universe. Principles and laws such as the inverse-square law and the laws of thermodynamics have held up so well under independent repeated testing by independent observers that we are as close to certain about them as we ever reasonably can get about anything.
If energy really did work the way energy healers claim they operate, then the inverse-square law and the laws of thermodynamics would fail so spectacularly that the world around us would look very different from how it actually does. The fact that we can rely so reliably on these laws means that what the energy healers claim cannot be true--it is a clear decision point, where you have to make the decision whether you accept or deny material physical reality.
Here's a couple of examples of how the universe around us would be very different if energy healing claims were true. Many energy healers claim that it does not matter how far away they are from the person they have intent to heal--that it's the same whether they're in the same room, or half a world away.
Have you ever been to a bonfire on a cold night?
Source: http://upload.wikimedia.org/wikipedia/commons/a/ac/Christmas_bonfire.jpg accessed 9 August 2012
A fire, among other things, is heat energy and light energy.
Did you get close, so that it felt very, very hot? Did you get further away from the fire, far enough so that you could feel the cold night air? You didn't have to get very far away for that experience, did you? The heat and light energy from the fire drops off very quickly as you get further away.
Source: http://upload.wikimedia.org/wikipedia/commons/2/28/Inverse_square_law.svg accessed 9 August 2012
Would the effect of the fire be the same, whether it was in the same room, or half a world away?
What kind of reasoning are we practicing here?
Heat energy quickly gets less effective as we get further away from the source; light energy quickly gets less effective as we get further away from the source, therefore, if energy healing is really based on energy, we expect it to quickly get less effective as we get further away from the source.
We are going from different examples of energy to derive a universal principle applying to all energy, so what kind of reasoning is that?
Now that we have derived that universal principle, we apply it in the following way:
The effect of physical energy falls off quickly with increasing distance from the source of the energy.
Energy healers claim that what they practice is not affected by distance from them as the source.
Therefore, what energy healers practice is not physical energy.
In applying the general principle about energy to a particular example, what kind of reasoning are we practicing there?
So--since they can't both be true at the same time--which one is right?
Are the energy healers right, and every bit of physics knowledge multiple independent researchers have built up over centuries wrong?
Or is the physics knowledge right, and the energy healers' explanations wrong in some way?
Since you have to choose only one of them, which possibility is more plausible: more likely, more reliable, and more believable?
Understanding these ideas--that not everything can simultaneously be true, that you really do have to choose between what is true and what is false, that scientific knowledge is never 100% certain but can at times get very close to that ideal--lays the groundwork for understanding the next form of logical reasoning we'll discuss.
Abductive reasoning is sometimes called "reasoning to the best explanation", and we'll look at how that works.
Abductive reasoning is difficult to describe concisely, or to teach, because it depends so much on what went before it. To use abductive reasoning, you have to have a solid multidisciplinary knowledge base.
If you don't have that, then, from the outside, it looks like you're making things up, or changing the rules arbitrarily or unfairly.
That's not really what's happening, but you can feel compassion for people who think that, because they don't see the entire process going on. It's like watching a far-away rock climber--you see them going in progression from hold to hold, but you don't see all the information they have up close that they are basing their decisions on in the moment.
And you can't just teach it easily, because it's not like a vending machine, where you always put the exact information in, and you get exactly the same answer in return.
These aspects of abductive reasoning can make it challenging, both to observers outside the process, as well as to learners trying to come to grips with carrying it out. We can certainly sympathize with frustrations at that challenge, yet all we can do is to try to connect the dots, and be as transparent as possible about the process, to assist those who come along afterwards in understanding why decisions are made in the way they are.
If you don't care where you're going, it doesn't matter which way you set out.
If, on the other hand, you care about going to the "best" explanation, then you have to know what that means in order to plan your journey to get there.
It's a complex question, not one that we can just answer by rote. Let's work through it by examples, and try to get larger principles out of those examples for the next situation that comes along.
Just like we had the classic "Socrates is a mortal" and "All swans are white" examples for deductive and inductive reasoning, there is a classic example of abductive reasoning that we can share with generations of people who studied these questions before us.
"The lawn is wet, so it must have rained last night" is an example frequently used to show abductive reasoning.
We have an observable, empirical, tangible fact: the lawn is wet.
We don't know why the lawn is wet, so we try to draw a hypothesis to account for our observation. There are many possibilities that could become hypotheses:
It could have rained last night.
Someone could have poured water on the lawn, accidentally or on purpose.
A passing water truck could have sprung a leak.
There are lots of other possibilities as well, limited only by our imaginations.
If all of those possibilities are equally good as explanations, then we are stuck--we remain unable to develop a causal explanation that we can then test to see whether or not that explanation is correct.
But not all possibilities are equally good as explanations--some are ruled out by patterns in our observation.
Others are ruled out, as we saw with the energy-healing claim, by centuries of shared human knowledge about the way the physical universe works--for those explanations to be true, our universe would have to look and act totally different than it does now. So we can rule out explanations like that as well, never with 100% certainty, but with enough certainty to operate on for now.
Starting out as a brand-new student in first grade at the age of 6, I was absolutely, madly, deeply in love with my teacher, Miss Kirby. I would have done anything at all to get her to think highly of me.
So I told her about my brand-new baby brother that my parents brought home from the hospital. She was very interested to hear that I was now the big girl in the family, and told me that I must be very proud.
I assured her that I was really a very good big sister.
I told her about how my baby brother escaped from his crib after my parents brought him home, and how he climbed a tree and got stuck up there, and how I had to go rescue him.
I told her I saved my little brother all by myself, and Miss Kirby reassured me that I was, indeed, a very good big sister.
Not long after that, my parents and I were at the grocery store, where we ran into her doing her own shopping. She asked my parents about the new addition to the family, and that's when the facts came out: there was no new little brother. I had just made the entire story up to impress her, and make her think I was strong and brave.
Which explanation more plausibly accounts for the facts of the matter?
Unlike any other newborn in the history of the human race, my infant baby brother really had the cognitive skills to formulate an escape plan, and the motor skills to climb out of the crib, let himself out the door, and then climb a tree, or
A little girl who doesn't know much about infant development tells a lie that makes herself look like a hero, in order to impress an adult whom she loves, and who she wants to think she is a very good girl.
(Just to complete the story, I'll mention that no punishment ensued from this either at school or at home. All of the grownups understood why I had told that lie, and dealt with it in constructive ways that supported me in not needing to tell lies anymore just to impress beloved adults.)
To figure out how plausible something is--not either a "true" or "false" answer, but values along a spectrum from "more plausible" to "less plausible"--you can't just look at it in isolation. You have to evaluate how well it fits into the integrated whole of everything else we know about.
Abductive reasoning, getting at the best explanations for facts, draws on that plausibility as one of the pillars that supports it.
To be able to evaluate that plausibility, we need to have a large, solid, and interdisciplinary knowledge base, and to know how the parts of that knowledge base integrate seamlessly with one another.
This is not an easy task, and it can't just be reduced to vending-machine science. That's why it can look to people who are not in on the process as if scientists are making arbitrary choices about what they accept and what they reject. The scientists are making choices among possibilities, but unless you are close up to the process, you can't see the details of how they're doing it.
The choices aren't arbitrary, but neither can they be easily summed up in a single concise one-size-fits-all formula, either.