PHIL1012 INTRODUCTION TO LOGIC
PROBLEM SET 7 (S2 2021)
Submit your answers to Problem Set 7 via Canvas before 23:59, Wednesday of Week 10.
1. Determine using a tree whether the following two propositions are equivalent. If they are
not equivalent, read off from your tree a model in which one proposition is true and the other
is false.
∀x(Px → Gc)
∀xPx → Gc
2. Determine using a tree whether the following argument is valid. If it is not valid, read off
a counterexample from your tree.
∀y(Fy → ¬Gy)
Ga ↔ ∃w¬Hw
∴ ¬Hb → ¬∀xFx
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