What is logic?
Answer: Propositions, and relationships between them.
- Consistency
- Consequence
- Equivalence
Example Propositions
A sentence expresses a proposition if it makes some statement about how things are.
- We have students from all over the world.
- There is no difference between the mind and the brain.
- 3 + 5 < 4 + 3. (Statement could be false)
Not all sentences express propositions.
- Please don't watch these lectures while driving a car.
- What is the capital of Ethiopia?
- Thank goodness; the poor cat!
- Hi, Jen!
How do we tell which sentences express propositions
A proposition is the kind of thing you could:
- believe or disbelieve;
- agree or disagree with;
- assert of deny;
- give a reason for or against;
- use as a reason for or against something else;
- and express with a declarative sentence