Argument from Silence
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[edit] Definition
Argument from Silence is an informal logical fallacy where a positive conclusion is drawn from someone's silence. For example, if one's opponent in a debate does not respond to an argument, it would be a fallacy to conclude that he or she cannot counter the argument. Especially on web forums, this is a fallacy because there are many other reasons why a particular respondent might not want or be able to respond. Reasons include hardware failure, scheduling, or a simple lack of desire to continue an obviously fruitless discussion. Another example of an argument from silence is concluding that a speaker or writer must be ignorant of something if he or she is silent about it.
[edit] Examples
Example:
- Antagonist: And we can see how space aliens have so thoroughly taken over our economy by the fact that ice is heavier than liquid water.
- <long period of non-response>
- Antagonist : Obviously, no one can rebut my claim about space aliens!
[edit] Exceptions to the Rule
In some areas, the maxim "Silence gives consent" is acceptable, but generally only under circumstances where a person has a specific duty to respond. For example, some legal jurisdictions hold that
"[a]ll material facts set forth in the statement required to be served by the moving party will be deemed to be admitted unless controverted by the statement required to be served by the opposing party." [US Federal Rules of Civil Procedures, Rule 56(c)]
As with issues of burden of proof, the standards of legal reasoning are not typically appropriate to informal (or even formal) debates.
Also, while the following may be called an argument from silence, it is not, strictly speaking, incorrect:
- Major premise: If X is silent about Y, then X is ignorant of Y.
- Minor premise: X is silent about Y.
- Conclusion: X is ignorant of Y.
Provided that it can be established that the major premise is in fact true, the argument is valid. The classic example of this is in the Sherlock Holmes story Silver Blaze, where Holmes notes the dog that didn't bark when it was expected to. The catch is that one has to rule out all the possible reasons besides ignorance that could lead X to be silent. Alternatively, if one is arguing probabilistically, one still has to show that of the various possible reasons for X's silence, the most likely one is the ignorance of X. Depending on the nature of X and Y, the major premise may be difficult or impossible to defend.
