Incorrect reasoning, 7 letters
Non sequitur, ad hominem, etc., 7 letters
Invalid or incorrect reasoning, 7 letters
Mr. Spock's catchword, 9 letters
Not according to Mr. Spock, 9 letters
What Mr. Spock is not, 9 letters
Without rhyme or reason, 11 letters
Black cats and broken mirrors, e.g., 8 letters
Black cats, supposedly, 8 letters
Dark clouds, to some, 8 letters
Spilled salt and such, to some, 8 letters