Canceling Hypothesis
This is when a lack of evidence for a given hypothesis is explained away by the ad hoc introduction of a second hypothesis, which directly contradicts the original claim. This is especially popular among denialists and flat earth conspiracy theorists.
P1: Hypothesis X is true.
P2: Hypothesis X lacks evidence, or is presented with contradictory evidence.
C: Therefore, Hypothesis Y is true. (Which cancels out Hypothesis X)
Self-Sealing Proposition
This is when a claim is presented in such a way that any and all evidence brought against it can be dismissed as just being part of the cover-up.
P1: X is true.
P2: X lacks evidence, or is presented with contradictory evidence.
P3: A lack of evidence or a presence of evidence to the contrary means that X is being covered up in some way.
C: Therefore, X is true.
The self-sealing one is my parents in a nutshell.
!ping FOX-ANON