Thinking

# 3 brain games to practice deductive, inductive, and abductive reasoning

Take a closer look at the different types of reasoning you use every day.
Key Takeaways
• Reasoning — the act of thinking about something in a logical manner — is an important skill in nearly all pursuits.
• Some games are focused on specific types of reasoning, including deductive, inductive, and abductive reasoning.
• These games will challenge your reasoning skills, and help you become more aware of when you’re using a specific type of reasoning.

We use reasoning skills to navigate our world every day, whether we’re troubleshooting a maintenance issue with a car or simply trying to find a lost set of keys. But it’s probably rare that you consider which type of reasoning you’re using in any given situation.

You might benefit from taking a closer look at the most common types of reasoning. These include deductive reasoning, where definitions give us certain truths; inductive reasoning, which uses observations to make probable generalizations; and abductive reasoning, which looks for causes. Each one has its own strengths, weaknesses, and situations where it works best.

There are ways to practice your reasoning skills — and not all of them involve cracking open a doorstopper of a philosophy textbook. Here, we look at some games that require various types of reasoning and show you the methods behind them.

## Deductive reasoning: 20 questions

Deductive reasoning starts with general statements and draws more specific, logically guaranteed inferences from them.

A famous example is:

A1: All men are mortal

A2: Socrates is a man

Therefore:

B: Socrates is mortal.

The two propositions, “Socrates is a man” and “All men are mortal,” are both true and, when combined, logically lead to the conclusion. Because the propositions are both true and the argument is properly structured (in this case, a syllogism), we say it is valid and sound. Therefore, we can be certain that Socrates is mortal. Sometimes errors are made, but when done properly, we can be sure of the truth.

A famous game that requires deductive reasoning is 20 questions. For the unfamiliar, the game involves at least two players: an answerer and a questioner. The answerer selects something that the questioner must deduce the identity of using 20 or fewer yes-or-no questions. The answerer cannot lie. If the questioner can determine what the answerer is thinking of, they win.

Each question gives the asking player a new proposition they know to be true. To win the game, they must both collect relevant information and be able to combine it properly. If they cannot do so, they lose.

## Inductive reasoning: Eleusis

Inductive reasoning is based on specific observations that are then generalized. Its generalizations are not guaranteed to be true, but they can be excellent working hypotheses if the data behind them is extensive enough. Larger data sets lead to better hypotheses.

An example of inductive reasoning is:

Data: All firetrucks I’ve seen are red

Generalization: Most firetrucks are red.

Of course, because this reasoning is based on generalized data sets, it cannot give us certainties, only increasingly likely truths. Moreover, sometimes a single data point will shatter the most established “truths.” For example, it was once thought that all swans were white. European scientists accepted this as true until they visited Australia and observed black swans.

Eleusis is a card game that relies on inductive reasoning. Invented by Robert Abbott in 1956, the game has one player who invents a rule about how cards must be laid on a table which the others must try to learn by collecting data. On their turns, players add cards to the table. If they do so in line with the secret rule, they stay. If not, they are removed and the player draws cards. The goal is for players to place their entire hand on the table and have no cards remaining.

To do so, they must experiment and determine the rules from ever-growing data sets. The game and its variants are often used to explain the scientific method.

## Abductive reasoning: Bulls and Cows

Formalized by the philosopher and mathematician Charles Peirce at the end of the 19th century, abductive reasoning looks for explanations from incomplete observations and some background knowledge.

You likely encounter abductive reasoning when you go to the doctor for a diagnosis. The doctor considers your symptoms and then concludes what the most likely cause for them is. For example, if I go in with a stomach ache, bloating, nausea, and a love of ice cream, they are likely to suggest lactose intolerance as a cause. While other causes still exist (I could have an ulcer, for example), abductive reasoning tells us to focus on the most likely solution.

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(A more technical way to think of abductive reasoning is to frame it as a deductive syllogism where the first premise is known, but the second one and the conclusion are merely likely.)

Abductive reasoning cannot give us certainties. However, it can provide explanations backed by evidence. Therefore, it is best to keep to the simplest and most probable explanation possible when using it.

Code-breaking games, like Bulls and Cows, Mastermind, or Worldle, rely on abductive reasoning. In each game, the player attempts to crack a code with known parameters and incomplete data. The player has to work backward from what limited information they start with and receive after each guess to determine what code would align with it and the game’s rules.

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