Abductive reasoning is a form of reasoning based on the formation and evaluation of hypotheses using the best available information. In many cases, it is synonymous with "educated guessing," the process of guessing based on a reasoned analysis of available information. Abductive reasoning starts with the observation of a phenomenon for which one does not have an immediate, clear explanation. One can then use this form of reasoning to develop an explanation that is sufficient to describe the observed phenomenon, though it must be noted that, without further testing, this explanation is only sufficient, not necessarily accurate. Abductive reasoning is useful in developing hypotheses to be tested, but it is also used for various purposes in artificial intelligence, philosophy, and a variety of other fields.
Deductive, inductive, and abductive reasoning are the three most widely used and most useful forms of reasoning. Deductive reasoning involves reasoning from a general rule to a specific conclusion. Inductive reasoning involves developing the most likely general rule from a set of specific observations. Scientific experimentation, which tends to involve observing controlled phenomena to determine rules of physical behavior, is based on inductive reasoning. Abductive reasoning is similar to inductive reasoning, but only involves developing a guess based on what limited data is available at a given time, before detailed testing and rigorous observation.
Many of the most important applications of abductive reasoning are in the day-to-day decisions that almost all people need to make. Most people do not have the time or energy to embark on a detailed scientific investigation before making a given decision, so they use their available knowledge to choose the best course based on educated guesses. Jurors, for example, use such reasoning when making decisions in court, as they must rely on the best available evidence, which is usually not enough to be considered scientifically sufficient for conclusive judgment. Even medical professionals use this form of educated guesswork when making decisions based on diagnostic testing results.
Scientists commonly use abductive reasoning to develop hypotheses to test. A cell biologist who witnesses an interesting change in an organism's eye color after widespread genetic mutation may, for instance, use his available knowledge to develop a guess about which gene is responsible for the color change. Instead of random genetic experiments, he can then focus his work on the gene he suspects is the most relevant. Without abductive reasoning, on the other hand, he would likely not even have this limited guidance.