Professor Chen: in the early Middle Ages, there was no trade between Europe and East Asia, because there were no written records in the existing archives  Researcher Li: your argument is similar to this one: the legendary Himalayan Snowman does not exist, because no one has ever witnessed this kind of snowman
The problem with this argument is that someone who sees a snowman can certainly prove that the snowman exists, but no one can't prove that the snowman does not exist
There is comparability between the arguments of different contents.