Introducing Logic Quotes

“I see nobody on the road,” said Alice. “I only wish I had such eyes,” the King remarked in a fretful tone. “To be able to see Nobody!”
― Dan Cryan, Introducing Logic: A Graphic Guide

“Russell’s point is that if the set is a member of itself, then by definition it can’t be a member of itself. But if it is not a member of itself, then it is a member of itself. So it is both a member of itself and not a member of itself. And that is a contradiction. This glaring mistake, allegedly, left Frege a broken man.”
― Dan Cryan, Introducing Logic: A Graphic Guide

“The great advantage of the reductio method is that it allows us to tell if a statement is true, even if we do not know how to construct a proof for it. We can tell a statement is true by showing that its negation leads to a contradiction.”
― Dan Cryan, Introducing Logic: A Graphic Guide

“Discovering Tautologies Logical symbols may be used in combination, which can help us calculate the truth condition of any logically complex sentences. For example, “p v ¬p”, which produces the following Truth Table:   When a formula only has T’s under it in a Truth Table, it means that it is true in all situations. The sentence “Either it is raining or it is not raining” cannot be false. Logicians call this a tautology. In a tautology, one truth follows from another of necessity only because of the logical syntax. So we know that any sentence with the same logical syntax will always be true. This”
― Dan Cryan, Introducing Logic: A Graphic Guide

“only because language has something in common with the world that it can be used to picture the world, so it is only because of logic that our sentences have meaning at all.”
― Dan Cryan, Introducing Logic: A Graphic Guide

“ALL PROPERTY IS THEFT. SO ALL THEFT IS PROPERTY.
THEREFORE THESE PEARLS ARE MINE.

This is clearly rubbish because there is nothing to link the truth of the conclusion to the truth of the supporting claims. What we need is to ensure that the truth of the supporting claims is preserved by the argument. Logic is quite simply the study of truth-preserving arguments.”
― Dan Cryan, Introducing Logic: A Graphic Guide

“Gottlob Frege’s Begriffsschrift.”
― Dan Cryan, Introducing Logic: A Graphic Guide