To which we add another wrinkle: many arguments, asserting the premises and the conclusion,
do not maintain that the premises' truth NECESSITATES the conclusion's, but only
that the premiss supports the conclusion, provides ground or reason to believe it's true.
Such arguments aren't valid, but it's inapt to call them invalid, as they aren't
meant to be deductive.

So many arguments given these days for God's existence do not claim to prove it,
but only to make it more plausible and perhaps to have cumulative force.
Same goes for arguments for implausibility--they don't claim to disprove
anything but only to  show that a certain thesis is unlikely.

Of course the whole field of inductive argument, probability theory, is found here.