Conditional and Biconditional Statements in Logic
1. Conditional Statement
A conditional statement expresses a relationship between two propositions where one depends on the other. It is often written in the form:
“If P, then Q“
- Symbolically: P→Q
- Read as: “If P, then Q.”
Examples:
- If it rains, then the ground will be wet.
- If a number is even, then it is divisible by 2.
Truth Table:
P (If) | Q (Then) | P→Q (True?) |
---|---|---|
True | True | True |
True | False | False |
False | True | True |
False | False | True |
2. Biconditional Statement
A biconditional statement expresses a relationship where both propositions are mutually true. It is often written as:
“If and only if P, then Q“
- Symbolically: P↔Q
- Read as: “P if and only if Q.”
Examples:
- A figure is a square if and only if it has four equal sides and four right angles.
- You will pass the exam if and only if you score at least 50%.
Truth Table:
P | Q | P↔Q (True?) |
---|---|---|
True | True | True |
True | False | False |
False | True | False |
False | False | True |
Key Differences
Feature | Conditional (P→Q) | Biconditional (P↔Q) |
---|---|---|
Meaning | Q follows from P | P and Q imply each other |
Dependency | One-directional | Bi-directional |
Key Phrase | “If… then…” | “If and only if” |