Back to topics

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?

Start reading

Ready to try your ideas aloud?

Your topic carries over. Record up to 2½ minutes, depending on your plan.

Ethics and philosophy

Deduction and induction make different kinds of claim

Deduction asks what must follow from stated premises, while induction uses observations to suggest what may happen next. A valid deduction still needs true premises for a true conclusion; further observations can overturn an inductive generalization.

3–5 min

Deduction and induction make different kinds of claim

Ethics and philosophy3–5 minDeduction asks what must follow from stated premises, while induction uses observations to suggest what may happen next. A valid deduction still needs true premises for a true conclusion; further observations can overturn an inductive generalization.

Ethics and philosophy

Why does the trolley problem change when you change how someone is saved?

A runaway trolley threatens five people. Redirecting it onto a track with one person and pushing someone into its path can produce different moral reactions, even when the numbers match. Explore how intention, duties, and using a person as a means influence the judgment.

3–7 min

Why does the trolley problem change when you change how someone is saved?

Ethics and philosophy3–7 minA runaway trolley threatens five people. Redirecting it onto a track with one person and pushing someone into its path can produce different moral reactions, even when the numbers match. Explore how intention, duties, and using a person as a means influence the judgment.

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