specious /ˈspiːʃəs/ adjective
Meaning
Superficially plausible, but actually wrong
Seeming to be right or true, but actually incorrect
Etymology
Latin
species > speciosus (fair) > specious (beautiful)
Estimated First Use
Late 1400s
Example
The impossible often has a kind of integrity to it which the merely improbably lacks. How often have you been presented with an apparently rational explanation of something that works in all respects other than one, which is that it is hopelessly improbable?…The first idea merely supposes that there is something we don’t know about, and…there are enough of those. The second, however, runs contrary to something fundamental and human which we do know about. We should therefore be very suspicious of it and all its specious rationality.
Douglas Adams, The Long, Dark, Tea-Time of The Soul, 1988