Belief bias
The tendency to judge an argument by whether we agree with its conclusion instead of by whether its reasoning holds up. A weak argument seems strong if its conclusion sounds believable to us.
In everyday life
People accept 'All flowers need water; roses need water; so roses are flowers' as logical because the conclusion is true, though the reasoning is broken.
In a debate, you rate the side that reaches the conclusion you already hold as 'more logical,' though a teacher later shows its reasoning had a clear gap and the other side's did not.
Why your mind does this
Simple, clear options are faster to understand and easier to act on, and when time is short that speed matters. Known odds and complete information feel safer because they let us predict what will happen. Preferring the clear option often saves effort that would be wasted on puzzles we can't solve.
Its family, in 30 seconds: Simple & complete
How to spot it
Ask whether you would accept the same reasoning if it led to a conclusion you dislike.
How to counter it
Test an argument's logic by swapping in a conclusion you disagree with and checking whether the steps still work.