What was the question for this implicit rationale, and corresponding answer?
There is no way to know that he fisherman is rowing backwards.
 The answer: it is not possible to tell
The question: Premise: "A fisherman is inside of a boat rowing while a bird is perched on the front of his boat."
Hypothesis: "The fisherman is rowing backwards while a bird is perched on the front of his boat."
Do we know that the hypothesis entailed by the premise?