LessonsNazar, the Movements of Thought, and the Need for LogicQuiz

Understanding the inferential form of the world/change example is different from proving the truth of its premises.

If both premises are true in the intended senses, that form entails the conclusion. But entailment by itself does not show that the premises are actually true.

Example: Every bird is a stone; a pigeon is a bird; therefore a pigeon is a stone. The formal pattern is valid, but the first premise is false, so this is not sound knowledge of the world.

Logic must distinguish what follows from assumed premises from whether those premises are true.

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Valid form and true premises are different

Nazar, the Movements of Thought, and the Need for Logic

Understanding the inferential form of the world/change example is different from proving the truth of its premises.

If both premises are true in the intended senses, that form entails the conclusion. But entailment by itself does not show that the premises are actually true.

Example: Every bird is a stone; a pigeon is a bird; therefore a pigeon is a stone. The formal pattern is valid, but the first premise is false, so this is not sound knowledge of the world.

Logic must distinguish what follows from assumed premises from whether those premises are true.