physics

John A. Leslie

John A. Leslie is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand John A. Leslie rather than just read about it. In short: John Andrew Leslie (born 2 August 1940) is a Canadian philosopher and writer. Biography Leslie was educated at Wadham College, Oxford, earning his B.A. in English Literature in 1962 and his M.Litt. in Classics in 1968.

Key takeaways

John A. Leslie belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect John A. Leslie to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of John A. Leslie from memory before moving on to harder problems.

Reference excerpt

John Andrew Leslie (born 2 August 1940) is a Canadian philosopher and writer.

Biography Leslie was educated at Wadham College, Oxford, earning his B.A. in English Literature in 1962 and his M.Litt. in Classics in 1968. He is currently Professor emeritus at the University of Guelph, in Ontario, Canada. In his book Universes, Leslie describes a philosophical parable in which an individual survives a firing squad of fifty expert marksmen unscathed. He offers two explanations for this remarkable event: either it is a fortuitous outcome, to be expected occasionally by pure chance among many thousands of attempted executions by firing squad; or it is intentional. Francis Collins references this parable in his book The Language of God: A Scientist Presents Evidence for Belief as part of his argument that the Anthropic Principle strongly suggests a Creator with intent.

Leslie has spoken as follows about his life's work: What I have to contribute is some technical defense of the idea that if you had an infinitely rich [universe], it could be explained by reference to its value. Its goodness could be the creative force which had produced it. I think if I would like to be remembered as a philosopher for any one thing, that would be the thing I'd most like to be remembered for.

Pantheism Leslie is a pantheist. His philosophical work takes influence from David Lewis, Plato and Spinoza. In his book Infinite Minds: A Philosophical Cosmology (2001), Leslie argues for a pantheistic universe in which everything exists in a divine mind. Philosopher Brendan Sweetman commented that the book promotes a "highly speculative, pantheistic theory that is fascinating in its own way, but that will probably convince very few." Leslie's book is unique because he accepts and uses arguments for the existence of God which are usually used to support theism such as a version of the cosmological argument and the design argument based on fine-tuning, but he explains these in a pantheistic way.

Selected publications Value and Existence (1979) Universes (1989) Physical Cosmology and Philosophy (1990) The End of the World: The Science and Ethics of Human Extinction. (1996) Modern Cosmology and Philosophy (1998) Infinite Minds: A Philosophical Cosmology (2001) Immortality Defended (2007) The Mystery of Existence: Why is there Anything At All? (2013) What God Might Be (2018)

See also Axiarchism – a term invented by John Leslie for the metaphysical belief that the world is largely or entirely determined by what is ethically valuable, and that things in this world have an intrinsic desire for the good Doomsday argument – a probabilistic argument that claims to predict number of future members of the human species given only an estimate of the total number of humans born so far Hostage Chess – a chess variant invented by Leslie

References

External links Personal homepage at University of Guelph Bio page at the Lifeboat Foundation Video of debate/discussion with John Leslie and Jim Holt on Bloggingheads.tv

Illustrations

Worked examples

Example 1 — a first encounter with John A. Leslie

Start with the simplest possible case. Write down what John A. Leslie claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to John A. Leslie before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about John A. Leslie ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of John A. Leslie

In research: John A. Leslie appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses John A. Leslie in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: John A. Leslie is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1940 births, 20th-century Canadian philosophers, 21st-century Canadian philosophers, so understanding it makes those chapters shorter.
In everyday life: Look for John A. Leslie outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study John A. Leslie in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what John A. Leslie means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain John A. Leslie out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is John A. Leslie in simple terms?

John Andrew Leslie (born 2 August 1940) is a Canadian philosopher and writer. Biography Leslie was educated at Wadham College, Oxford, earning his B.A. in English Literature in 1962 and his M.Litt. in Classics in 1968.

Why does John A. Leslie matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study John A. Leslie?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on John A. Leslie.