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Could your memories prove that yesterday existed?

A diary and a memory both exist in the present, even when they refer to yesterday. Bertrand Russell’s five-minute-world thought experiment asks what would happen if a fictional alternative reproduced all that present evidence, without treating that alternative as a serious history of the world.

3–5 min

Questions you could explore

  • Is ruling out every imaginable alternative the same as having good evidence?
  • What does a thought experiment reveal if it cannot be tested?

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Ethics and philosophy

When does a conclusion follow, and when is it a prediction?

A rule can tell you what must follow if its premises are true. A pattern in observations can suggest what you may find next. Deduction and induction make these different kinds of move: a valid deduction still needs true premises, while further observations can overturn an inductive generalization.

3–5 min

When does a conclusion follow, and when is it a prediction?

Ethics and philosophy3–5 minA rule can tell you what must follow if its premises are true. A pattern in observations can suggest what you may find next. Deduction and induction make these different kinds of move: a valid deduction still needs true premises, while further observations can overturn an inductive generalization.

Ethics and philosophy

Why can two trolley dilemmas feel so different?

Two imagined choices can save the same number of people yet feel morally different. Redirecting a runaway trolley and using a person to stop it raise questions about intentions, duties, and whether a good result can justify the means.

3–7 min

Why can two trolley dilemmas feel so different?

Ethics and philosophy3–7 minTwo imagined choices can save the same number of people yet feel morally different. Redirecting a runaway trolley and using a person to stop it raise questions about intentions, duties, and whether a good result can justify the means.

Ethics and philosophy

Is the red you see the same red that I see?

We can agree that a tomato is red and choose the same matching paint. Does that agreement show that red feels the same to each of us? The puzzle separates what we can compare publicly from what another person’s experience is like.

4–6 min

Is the red you see the same red that I see?

Ethics and philosophy4–6 minWe can agree that a tomato is red and choose the same matching paint. Does that agreement show that red feels the same to each of us? The puzzle separates what we can compare publicly from what another person’s experience is like.

Could your memories prove that yesterday existed? | Speech Topic | speaking.app