An appeal to consequences states that something must be true or false because the consequences of it being such would be either negative or positive.
Example of Appeal to Consequences fallacy:
Premise 1: There should be some ultimate punishment for people doing bad things.
Premise 2: God punishes people for the bad things they do, even if they law doesn’t catch them.
Premise 3: Reality will respond to moral impetus.
Conclusion: God must exist.
The above argument is deductively valid. If all premises are true, then the conclusion would also be true, making it an informal fallacy.
Why it’s erroneous:
As with everything else on this site, we’re not commenting on whether or not the conclusion is ultimately true – only whether or not the premises support said conclusion.
In this instance, the consequences we either desire or fear cannot change the truth. The truth will always be what it is, regardless of consequence.