premise: A guy taking a nap in the back of a vehicle.
hypothesis: A man is dozing off while bumming a ride in the back of a truck.
explanation_1: The man is not necessarily bumming a ride and the vehicle may not be a truck.
explanation_2: Being in the back of a vehicle does not imply one is bumming a ride.  Not all vehicles are trucks.
explanation_3: There are many types of vehicle other than a truck and a man riding a vehicle may not be bumming a ride and dozing off is the act of going to sleep while taking a nap means one is already in one of the sleep states and a guy can be a boy or a man when used in the singular.
premise_logic: exists e1 x1 x2 x3 x4 x5.(n_back(x4) & a_topic(x1) & in(e1,x4) & of(x4,x5) & n_vehicle(x5) & Theme(e1,x3) & Actor(e1,x2) & v_take(e1) & n_nap(x3) & (x1 = x2) & n_guy(x1))
hypothesis_logic: exists e1 e2 s1 x1 x2 x3 x4.(n_back(x3) & while(e1,e2) & Theme(e2,x2) & Actor(e2,x1) & v_bum(e2) & in(x2,x3) & of(x3,x4) & n_truck(x4) & n_ride(x2) & a_off(s1) & Manner(e1,s1) & Actor(e1,x1) & v_doze(e1) & n_man(x1))
premise_sim: exists e1 x1 x2 x3 x4 x5.(v_take(e1) & of(x4,x5) & n_vehicle(x5) & n_nap(x3) & n_guy(x1) & n_back(x4) & in(e1,x4) & a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & (x1 = x2))
hypothesis_sim: exists e1 e2 s1 x1 x2 x3 x4.(while(e1,e2) & v_doze(e1) & v_bum(e2) & of(x3,x4) & n_truck(x4) & n_ride(x2) & n_man(x1) & n_back(x3) & in(x2,x3) & a_off(s1) & Theme(e2,x2) & Manner(e1,s1) & Actor(e2,x1) & Actor(e1,x1))