“Hypervigilance sounds innocuous” this is a casual claim. This statement assumes that the reader believes that hypervigilance sounds innocuous. However anyone in the field of medicine, PTSD sufferer, family of said PTSD sufferer, and friends of said PTSD sufferer would most likely know what hypervigilance is, so, to assume that would be slightly disingenuous.
“Imagine there’s a murderer in your house. And it is dark outside, and the electricity is out. Imagine your nervous system spiking, readying you as you feel your way along the walls, the sensitivity of your hearing, the tautness in your muscles, the alertness shooting around inside your skull. And then imagine feeling like that all the time.” this is an analogous claim that tries to show how someone with PTSD would feel all the time compared to a normal human being in this certain scenario.
“Imagine there’s a murderer in your house.” This is a casual claim. The author is assuming that the reader can imagine. This most likely is possible, however there is condition called Aphantasia that doesn’t allow people the ability to create images within there mind. This would mean that for the people that do suffer from this condition that they wouldn’t be able to imagine such a scenario.