what is deductive reasoning

What is deductive reasoning?

September 5, 2023
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Have you ever heard of something called deductive reasoning?

Even if you haven't heard of it, there’s a good chance you do it every single day.

Deductive reasoning is a logical type of deductive inference—or a way of thinking that helps you figure out things in a logical and smart way. In simpler words, deductive reasoning helps you make smart guesses based on what you already know is true. 

Want to discover more about it and how can you improve it? Keep reading to learn more. 

What is deductive reasoning?

Imagine you have a bunch of puzzle pieces (these are facts or information). You also have a picture on the puzzle box (this is a general rule). Then you use these puzzle pieces to create the picture just like on the box. 

Deductive reasoning starts with these general rules or facts that we believe are true. Then, we use these rules to come up with inferences based on new ideas or conclusions. If the rules are true, then the conclusion based on what you come up with must also be true. 

Here’s an example: Let’s say you know that “all cats have tails” and you also know that “Fluffy is a cat.” Using deductive reasoning, you can then conclude that “Fluffy has a tail.” This is because the rule says all cats have tails, and since Fluffy is a cat, she must have a tail. 

Deductive reasoning has three steps: 

Step 1: Starting with what you know: You begin with some things you believe are true. These things can be stuff you’ve seen, things you’ve learned before, or general conclusions. 

Step 2: Figuring something out: You can use these true things to figure out something new. This new thing should also be true if the first things are true. 

Step 3: Checking if it makes sense: Finally, you make sure that the new thing you figured out actually makes sense based on the true things you started with. 

Deductive versus inductive reasoning

There’s a chance you might have heard of inductive reasoning—but it’s not the same as deductive reasoning. Inductive and deductive reasoning are two distinct approaches to logical conclusion-making. 

Here are some key differences: 

Deductive reasoning is like starting with a big idea and using it to figure out smaller things, or having a rule and using it to solve problems. For example, if you know that “all fish live in water” and you also know “Nemo is a fish,” you can use deductive reasoning to figure out that “Nemo lives in water.” You’re using the general rule to find a specific answer. 

Inductive reasoning, on the other hand, is the opposite. You start with lots of specific things, like observations, and then you come up with a general idea based on those specifics. It’s like noticing a bunch of fish in water and then thinking, “Hey, maybe all fish live in water.” So, you’re using many examples to make a big idea. 

The main difference between deductive reasoning and inductive reasoning is that in deductive reasoning, you use a rule to solve puzzles or find specific answers, while with inductive reasoning, you spot patterns to come up with new ideas. Both are used to understand things better. 

Scientists often use both of these ways to learn about the world and make smart conclusions, but even if you’re not a scientist, you can too. 

The significance of deductive reasoning in daily life

Deductive reasoning is a useful tool you can use in everyday life to make choices and solve problems. And whether you realize it or not, you use deductive reasoning already when you think about things based on facts you know. 

For example, if it’s cloudy and you’re wondering whether to take an umbrella, you might remember that it’s rained a lot lately and think, “Maybe I should take the umbrella today.” You’re taking what you know and using it to make a decision. 

When things get tricky, like solving a puzzle or a tough question, deductive reasoning can help, too. You can break down the big problem into smaller parts and figure them out one by one. It’s like solving a big puzzle by focusing on each piece one at a time. 

Deductive reasoning is particularly important in professions such as law, where lawyers use it to draw conclusions from evidence presented in court. By applying deductive reasoning to the facts of a case, lawyers can build a logical argument that supports their client's position.

In science, deductive reasoning is used to draw conclusions from experiments and observations. Scientists use deductive reasoning to develop hypotheses and theories that can be tested through experimentation. By starting with a general set of premises, or principles, and using deductive reasoning to draw specific conclusions, scientists can develop a deeper understanding of the natural world.

The 3 types of deductive reasoning

There are three types of deductive reasoning: categorical deduction, propositional deduction, and predicative deduction. Let’s break them down: 

1. Categorical deduction: reasoning within categories

Categorical deduction involves putting things into groups and making smart decisions based on those groups. Imagine you have a rule like “all dogs bark,” and you know your pet is a dog. You can use categorical deduction to decide that your pet barks. This helps us in many jobs like law and science, where you need to make solid, evidence-based arguments and choices.

2. Propositional deduction: exploring if-then scenarios

Propositional deduction involves exploring if-then scenarios and drawing conclusions based on them. It’s like saying, “If I do my homework, then I can play games.” If you know that “if it’s sunny, the ground dries up,” and you see that the ground is dry, you can figure out that it must have been sunny. People use this technique in debates and discussions to make strong, persuasive points. 

3. Predicative deduction: drawing conclusions from premises

Predicative deduction involves looking at premises, or examples, to understand things better. So, if you know the premise that “all birds have feathers,” and you know Tweety is a bird, you can conclude that Tweety must have feathers. 

All of these types of deductive reasoning are really useful for making good decisions, solving problems, and learning more about the world.

Logically sound deductive reasoning: examples and analysis

So, let’s say you’re solving a puzzle. You have some facts handy, and you want to figure out something new. Logically sound deductive reasoning, or making conclusions based on true facts, helps you do that in a smart way, because it allows you to draw accurate conclusions based on factual information. 

But to understand deductive reasoning better, you need to look at how good these facts are—and this is done by analyzing the validity and soundness of deductive arguments.

Analyzing the validity and soundness of deductive arguments

The validity and soundness of a deductive argument are two important criteria for evaluating its quality. 

  • Validity: An argument is valid when the conclusion must be true based on the facts you have. It’s like putting puzzle pieces together in a way that fits perfectly. For instance, if you know “all roses have thorns” and “the flower you're holding is a rose,” it’s valid to say “the flower you're holding has thorns.”
  • Soundness: An argument is sound when it’s not only valid but is also based on true facts. So, if you can prove that “all roses have thorns” and that “the flower you're holding is a rose,” then this argument is both valid and sound because the facts are true. 

However, an argument can be valid but not sound if the facts are wrong. For example, if you think “all bears can fly” and “Teddy is a bear,” it’s I to say “Teddy can fly,” but it’s not sound because bears can’t actually fly. 

Logically unsound deductive reasoning: examples and explanation

Now, let’s say you’re imagining the same puzzle as before, but someone gives you the wrong pieces. Logically unsound deductive reasoning is like trying to make sense of things using those wrong puzzle pieces. It can lead you to wrong conclusions and isn’t a good way to think. 

Here’s an example: Let’s say someone tells you “all dogs have superpowers” and then says “Rover is a dog, so Rover has superpowers.” This is not a good way to think because, as much as we would love to see this in real life, the whole first part of the statement is wrong. 

Another example is when someone says “everyone who wears glasses is a genius” and then says “Emma wears glasses, so Emma is a genius.” This isn’t a good way to think either because not all people who wear glasses are geniuses. 

When you use false facts or make mistakes in your thinking, you can end up with wrong ideas, which may ultimately lead to confusion and bad decisions. To think clearly and make good choices, it’s important to do your homework and use true facts that fit together properly.  

Common mistakes in deductive reasoning and how to avoid them

Deductive reasoning is a great tool for critical thinking, but it’s also prone to several common mistakes. Here are a few and how to avoid them: 

  • Assuming that the premises are true without real evidence: To avoid this, always check if the facts are true before making a decision. 
  • Using invalid, or wrong arguments that don’t logically make sense: To fix this, use an intentional way of thinking that really fits the situation. 
  • Ignoring facts that don’t agree with what you think: To fix this, consider all sides of the story before making up your mind.
  • Using tricky ways of reasoning, such as circular reasoning or ad hominem attacks: To avoid this, always make sure your line of thinking makes sense. 

These mistakes can have a significant impact on the accuracy and reliability of deductive reasoning. 

Want to avoid these mistakes in the future? Here are our tips:

  • Check if the facts are true before believing them.
  • Use a way of thinking that fits the situation. 
  • Think about all the different ideas and facts. 
  • Use smart and clear ways of thinking, not tricky ones. 

Improving your deductive reasoning skills: practical tips

There are several practical tips for improving your deductive reasoning skills, including practicing regularly, being mentally flexible, and using games and activities that boost deductive reasoning. By honing your deductive reasoning skills, you can become a more effective problem solver and critical thinker.

5 useful strategies to enhance your deductive reasoning

Some useful strategies to enhance your deductive reasoning include:

  1. Breaking down complex problems into smaller parts to better understand the facts
  2. Considering all possible scenarios and counterexamples to ensure that the conclusion is accurate and reliable
  3. Using diagrams, charts, or other visual aids to help organize information and identify patterns
  4. Practicing regularly and consistently to build your deductive reasoning skills over time
  5. Being mentally flexible and open-minded to new ideas and perspectives

Engaging with fun brain games that boost deductive reasoning

Another strategy? Games. There are several games and activities that can help boost deductive reasoning, including the following:

  • Sudoku: Sudokus are number-based puzzle games that challenge your mind to think logically and systematically.
  • Crossword puzzles: Crossword puzzles are word-based puzzle games that require deduction and problem-solving skills.
  • Logic puzzles: Logic puzzles require you to use deductive reasoning to determine the correct sequence of events or relationships between objects.

All these games help improve deductive reasoning by challenging the mind to think logically and draw accurate conclusions from premises. Regular practice with these activities can help you build your deductive reasoning skills and become a more effective problem-solver and critical thinker.

Final thoughts on deductive reasoning: a tool for critical thinking

As you can see, deductive reasoning is a valuable tool for critical thinking. It helps you make smart decisions based on true facts. By learning about different types of deductive reasoning and avoiding common mistakes, you can get even better at solving problems and thinking really well.

Just like practicing a sport or playing an instrument, practicing deductive reasoning exercises help you get better at it. The more you practice, the better you become at using deductive reasoning effectively. And if you’re looking for an easy and fun way to do this, check out the Elevate app. 

With the Elevate app, you can make exercising your deductive reasoning skills a habit through personalized brain training workouts, plus 40+ games backed by science and designed to improve your vocabulary, mental math, memory skills, and more. 

Download Elevate on iOS or Android now, and start flexing your critical thinking muscles today!


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