Welcome back to the webref.org blog. We often talk about “common sense” or “logical thinking,” but what does that actually mean in a scientific context?
If the various branches of science (Natural, Social, and Computer Science) are the buildings of human knowledge, Logic is the foundation they are all built upon. It is the formal study of the principles of valid reasoning and correct inference. In short, logic is the “science of proof.”
What Exactly is Logic?
Logic is a branch of both Philosophy and the Formal Sciences. It doesn’t care about what is true in the “real world” as much as it cares about whether a conclusion follows correctly from its starting points, known as premises.
In a logical system, if your premises are true and your logic is sound, your conclusion must be true.
The Two Pillars of Logic
Most logical reasoning falls into one of two categories. Understanding the difference is the first step toward better critical thinking.
1. Deductive Reasoning
Deductive logic moves from the general to the specific. It provides absolute certainty. If the premises are true, the conclusion is inescapable.
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Classic Example:
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Premise A: All humans are mortal.
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Premise B: Socrates is a human.
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Conclusion: Therefore, Socrates is mortal.
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2. Inductive Reasoning
Inductive logic moves from the specific to the general. This is the logic used in most scientific experiments. It deals with probability rather than absolute certainty.
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Example:
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Observation: Every swan I have seen is white.
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Conclusion: Most (or all) swans are probably white.
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(Note: This can be overturned if you find one black swan!)
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Symbolic Logic: The Math of Thought
In modern logic, we often move away from words and use symbols. This allows logicians to map out complex arguments like mathematical equations.
The most basic tools here are Logic Gates (used in Computer Science) and Truth Tables. A truth table allows you to see every possible outcome of a logical statement to determine if it is always true (a tautology) or always false (a contradiction).
The Enemies of Reason: Logical Fallacies
A “fallacy” is a flaw in reasoning. Even if someone is right about their conclusion, if their logic is fallacious, their argument is weak. Recognizing these is a superpower in the age of misinformation.
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Ad Hominem: Attacking the person instead of the argument.
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Straw Man: Misrepresenting someone’s argument to make it easier to attack.
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Slippery Slope: Claiming that one small step will inevitably lead to a chain of disastrous (and unrelated) events.
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Confirmation Bias: Only looking for “logic” that supports what you already believe.
Why Logic Matters in 2025
Logic isn’t just for ancient Greek philosophers; it is the heartbeat of the 21st century.
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Programming: Every line of code in every app you use is a series of logical “If/Then” statements.
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Artificial Intelligence: Large Language Models (LLMs) are essentially massive engines of statistical logic.
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Critical Thinking: In an era of “fake news” and deepfakes, logic is the filter that helps you distinguish between a valid argument and an emotional manipulation.
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Debate and Law: The entire legal system is built on the rules of evidence and logical inference.
Final Thought: Soundness vs. Validity
In logic, an argument can be valid (the structure is correct) but not sound (the premises are false).
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Valid but Unsound: “All cats are invisible. My pet is a cat. Therefore, my pet is invisible.” The logic works perfectly, but because the first premise is a lie, the argument fails the “reality check.”
By studying logic, you learn to check both the facts and the structure of the world around you.