Arrant- complete, utter
Ex: “Only an arrant fool would believe that we are alone in the universe. For one, just take a second to imagine the overwhelming vastness of space. For two, just take a minute to comprehend the super bigness of that which is not earth. For three, envision our planetary home and its smally smallness and consider that in this tiny, tiny ball of rock there are living things! And then compare that to outer space which is definitely larger than earth and even has other rocks floating in it that are- *begins to start counting with fingers*- potentially even more massive than earth, or at least the same size as us! Now close your eyes and imagine the pebble that we are on just drifting aimlessly, on no set course, through the emptiness of it all. We are bound to bump into a similar rock at some point, right?” – Guy who really wants to convince his friends of the existence of aliens but whose argument is that of a bumbling ass who has no knowledge of astronomy or even really just the basic info about our solar system. / Possibly schizophrenic man on the sidewalk who wants to educate some passersby on outer space/ A being from an extraterrestrial civilization that is about 500 years less advanced than us (or 1500 years- they may not have had the advent of the science-postponing Middle Ages on their planet) looking into the sky and musing on the possibility of life outside of his home planet.