Introduction to Logic

Fitch Proofs: Examples

The following four examples of proofs using the Fitch system have been worked out using the guidelines mentioned in Be-Fitched. You are encouraged to work out these problems by yourself before having a look at the solutions.

Examples of Fitch Proofs:

1. Prove q from the premises: pq, and ¬p. Solution
2. Prove pq from the premise ¬(¬p ∨ ¬q) Solution
3. Prove ¬p ∨ ¬q from the premise ¬(pq) Solution
4. Prove ad from the premises: ab, cd, and ¬b ∧ ¬c Solution

The above solutions were written up in the Fitch proof editor. This editor is also accessible from the Tools page in the course navigation bar.