SILENCE – Drawing a conclusion based on the silence of your opponent.
There are several reasons why people may not respond to you in a debate. They could be dumbfounded by how bad your argument is, they may not be familiar with the topic well enough, or they might not care to get into a debate for whatever reason. None of these strengthen your argument. Thinking that they do is the fallacy of Arguing from Silence.
One example of this fallacy:
Abe: You realize that if you support anything supplied by Koch Industries then you’re a virulent racist and are basically bringing this country one step closer to reinstating slavery.
Ben: (Stares quitely with mouth wide-opened).
Abe: Hah, I knew it! Even you libertarians cannot deny your overt racism.
The reality: Ben was probably wondering, “What is Koch Industries?” or “How could anyone follow such twisted logic to think that slavery will come back if I buy Dixie paper cups?”
A second example of the fallacy:
Anonymous Poster: I made such a great comment on the website ‘TheCitizenScholars.com’ that the author didn’t even respond! He must have conceded the point.
The reality: Sometimes it is not worth responding to every post. If the point was made, the argument isn’t advancing, and everyone else has lost interest, then it is simply a waste of time and effort.
Exception: In certain contexts, silence is suspicious. If you are on trial and under oath, a refusal to answer questions can weigh against you. This is not a fallacy.