As part of the first-ever Design Thinking for Legal Services class, we have the opportunity to write a number of blog posts of the BuildHours website.  These posts are geared toward our readings, class discussions, or class material. 

Below is my first post focusing on abductive reasoning and its role in the design-thinking process.


In Design Thinking, Abductive Reasoning allows a designer to develop a hypothesis based on all available evidence.  Legal professionals apply this skill daily.

Design thinking and legal analytical reasoning are two unique schools of thought.  But are they really?  There are many overlaps in how these two schools share  a common class: abductive logic.

Teaching this class would be the American philosopher Charles Sanders Peirce.  To Pierce, abducing a hypothetical explanation, X, from an observed circumstance, Y,  is to surmise that may be true because then Y would be a matter of course.

But what does that really mean?  In Peirce's own words, this is a method of describing how we "guess" about a circumstance.

In the legal context, all law students are taught to read a set of facts and to try and hypothesize about the most plausible explanation.  At its core, this is a form of abductive reasoning.  The law student is observing all available evidence and forming a hypothesis.  In legal abduction, the inference from effect to cause and the application of the known facts to the unknown is what drives a legal hypothesis.

In design"[it] is always about synthesis - synthesis of market needs, technology trends, and business needs."  During synthesis, designers organize, manipulate, prune, and filter gathered data into a cohesive structure for information building.  "Synthesis reveals a cohesion and sense of continuity; synthesis indicates a push towards organization, reduction, and clarity."

Synthesis is an abductive sensemaking process.  

Abductive logic allows for the creation of new knowledge or insight - C is introduced as  the best hypothesis for why B is occurring; however, C is not part of the original set of premises.

Design Synthesis is a way to apply abductive logic within the confines of a design problem. The constrains of the problem act as the logical "premises" and a designer's life experiences begin to shape the abduction.  As described by Peirce, "[t]he abductive suggestion comes to us like a flash.  It is an act of insight, although [an] extremely fallible insight.  It is true that the different elements of the hypothesis were in our minds before, but it is the idea of putting together what we had never before dreamed of putting together which flashes the new suggestion before our contemplation."

Because the design process is iterative, previous experiences help shape the evidence that goes into future abductions.  These abductions help shape the hypotheses that are applied to a design problem - most specifically at the "definition" stage.

As Roger Martin describes it, Abduction is the "logic of what might be."  It differs from deductive logic, which is the logic of what must be due to the fact that deduction reasons from the general to the specific.  Inductive logic, or the study of what is operative, reasons from the specific to the general.

Peirce's fascination with the "logical leaps of the mind" or the "flashes of inspiration" help drive a different process of applying all available evidence to hypothesize a problem.

As Roger Martin describes it, the best bet is to strive for a balance between induction, deduction, and abduction. A healthy diet of varied thought, especially in the definition of a problem, can lead to the most satisfying result.

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