People looking at fish at an aquarium.
The people are eating fish.
In sentence one the people are observing the fish in an aquarium. In sentence two they are eating fish. One is not able to consume the aquarium fish, thus making these sentences contradictory.
exists e1 x1 x2 x3.(at(e1,x2) & at(x2,x3) & n_aquarium(x3) & n_fish(x2) & Actor(e1,x1) & v_look(e1) & n_people(x1))
exists e1 x1 x2.(n_people(x1) & Theme(e1,x2) & Actor(e1,x1) & v_eat(e1) & n_fish(x2))