2019-12-24

## Are rules of replacement rules of implication?

Implication rules are valid argument forms that are validly applied only to an entire line. Replacement rules are pairs of logically equivalent statement forms (they have identical truth tables) that may replace each other within the context of a proof.

What are the parts of an implication?

The statement p in an implication p⇒q is called its hypothesis, premise, or antecedent, and q the conclusion or consequence.

### What are the properties of implication?

Implication has two properties which resemble the reflexive and transitive properties of equality. One, p=> p, is called a “tautology.” Tautologies, although widely used, do not add much to understanding. “Why is the water salty?” asks the little boy. “Because ocean water is salty,” says his father.

What is the difference between rules of inference and rules of replacement?

The main difference is that rules of inference are forms of valid arguments (that’s why they have a therefore ∴ symbol), but rules of replacement are forms of equivalent propositions (which is why they have the equivalence sign ≡ between the two parts).

## How many rules are rule of replacement according to Copi?

So long as each step is justified by reference to an earlier step (or steps) in the proof and to one of the nineteen rules, it must be a valid derivation. Next, let’s work with the third premise a bit: 1. A ∨ (B • ~C) premise 2.

How many rules of replacement are there?

We have ten such rules, which are called the rules of replacement. The difference between these two sets of rules is that the rules of inference are themselves inferences whereas rules of replacement are not. However, the rules of replacement are restricted to change or change in the form of statements.

### Why is denying the consequent valid?

Modus ponens is a valid argument form in Western philosophy because the truth of the premises guarantees the truth of the conclusion; however, affirming the consequent is an invalid argument form because the truth of the premises does not guarantee the truth of the conclusion.