Last year I wrote a post about abductive and adductive reasoning, and how they are important skills for innovation. A couple of months after I wrote it, I was in a discussion about the topic with someone who insisted that abductive reasoning is the only valid form of hypothetical reasoning. He pointed out that adductive reasoning isn’t listed in the Stanford Encyclopedia of Philosophy as evidence that it was an irrelevant term.
I had always thought that adductive thinking was not only relevant, but a necessary complement to abductive reasoning when speaking about hypothetical concepts. I'd like to go through my thought process for why it's relevant, and I'd love input from others about these ideas. For me it can best be summed up in a matrix to show how the types of reasoning relate to each other as I use them.
The matrix may be best explained with an example of Sir Isaac Newton’s apple tree.
If we start with the inductive and deductive reasoning boxes, we see that the inputs to both are real, observable, linear, and provide reliable outcomes. So, if we observe that when an apple gets detached from a tree, it falls straight to the ground, we could draw the following conclusions.
By using inductive reasoning we would create a rule stating that when apples detach from the tree they fall straight to the ground. We could also easily apply this rule to anything that is unsupported in the air, will fall straight to the ground.
By using deductive reasoning, we could draw the following conclusion. If an apple became detached from the tree and fell straight to the ground, and I was standing underneath the apple, it would hit me on its way down to the ground. The application of this conclusion is what would make us uneasy if we were to walk under a crane lifting a heavy block.
The inputs to creating both the rule and the conclusion are observable and real. We can reproduce these situations and achieve predictable, repeatable results, which we would call a highly reliable outcome.
This is the type of reasoning and measurement that is highly valued in areas of business that are responsible for delivering reliable results. But is this the type of reasoning that led Newton to develop the idea that some force from the earth may be pulling the apple toward it? As with most new ideas, inductive and deductive reasoning are necessary, but not sufficient, to develop radically new theories.
If inductive reasoning creates a rule for what is happening, ie: the apple falls straight down to the ground, abductive reasoning is seeking to explain why that rule is true, ie: why is the apple falling straight down to the ground? Different hypotheses could be developed to explain why this is happening. Further observation could add another rule: the apple is falling faster as it gets closer to the ground. This additional information could rule out some hypotheses, and support others. Eventually a theory is developed that seems to be a likely reason why all of these rules are true. In this case, that there is a force from the earth that pulls objects toward it, later to be known as gravity.
If this theory is true, then what else could we conclude? This is where adductive reasoning comes into play. Adductive reasoning seeks to find plausible new conclusions based on the reason why a rule is true. In other words, what else could be true if there actually was a force within the earth that pulled objects toward it? It is this type of thinking that leads to different applications of the laws of gravity, eventually enabling us to determine the effects of different gravitational fields on our planet and others.
Where inductive and deductive reasoning produce outcomes with a high degree of reliability, abductive and adductive reasoning produce outcomes with a high degree of validity. That is, rather than seeking to set up an experiment that will produce repeatable results, it is necessary to set up experiments that help us see different aspects of our hypothesis. It helps us to more fully describe phenomena that cannot be observed, and instead needs to be inferred. Ultimately it helps us to know whether one hypothesis answers our question or solves our problem better than another hypothesis.
By now two things must be pretty clear as to where I’m going with this. First, I do believe that adductive reasoning is different from abductive reasoning. I have observed people who are much better at one than at the other. I have also observed people who have trouble with hypothetical situations in any capacity. This tells me that all four types of reasoning require slightly different skills, aptitudes, and/or ways of perceiving the world, that they are equally necessarily, and that none alone are sufficient in gaining a full understanding of new ideas. Second, I hope that this sheds more light on why innovation is so difficult in many companies. If a company is (as most companies are) responsible for delivering reliable, repeatable products and services, then they will value inputs that are real, observable, and yield reliable outcomes.
However, even though the conclusions drawn from abductive and adductive reasoning are not linear, they are certainly not without logic. This is what is difficult for many to grasp. While the measures may not be the same for new ideas, there should still be measures that ensure the validity of one idea over another. And these measures will be different from those used to measure day-to-day processes.
Think of it this way. What could Newton have concluded if his boss had suggested that he sit under 1000 apple trees to prove “with statistical significance” that his observation was correct?